If we were to consider this contest as a trial, then clearly the first step would be the determination of what evidence is admissable. However, given that we're talking about sci-fi, we must also (and first) determine what constitutes evidence anyway.
For this purpose we pretend that the Empire and Federation are real, actual entities with technology that actually works, whether or not we understand how. We accept as true the fictional histories and facts of their natures and assume them to be internally consistent, in spite of whatever continuity errors or general peculiarities might have crept in. Further, it is assumed that the physics of both universes operate under the same basic principles and natural laws (the ones we know, or the ones we don't), so that, in effect, both universes/galaxies operate according to and within the same fundamental universal (but fictional) "reality".
In keeping with Usenet Vs. Debate tradition, the films/episodes of both, including the special effects, are assumed to be documentary-style footage of actual events, and -- barring obvious cutscenes, flashbacks, or slow-motion work -- it is assumed that the events from each scene generally occur in realtime.
There are limits to how far one can take this sort of analysis, of course. For one thing, the makers of Star Wars have often stated that Star Wars is not science fiction, but is instead "space fantasy" . . . implying that attempts to analyze Star Wars to produce a self-consistent understanding of its technology levels could be doomed to failure. However, given that the same is true of Star Trek at times (the best example being widely variable warp velocities, or just Star Trek: Voyager), we can take our best shot toward finding the most reasonable position.
Another potential pitfall is that, even today, there are many elements of even the most recently-produced Trek and Wars which seem almost anachronistic . . . as if societies hundreds of years more advanced had suffered technological regressions somehow. Of course, the truth is that there were often simply technological breakthroughs which were not known to the writers or else were ignored for "dramatic necessity". However, for the most part we can simply assume that both Trek and Wars technological history would include Earth-level technologies of the present-day (though I rather doubt that this sort of rationale can be maintained with a straight face much beyond circa 2025). Suffice it to say that in fifty years the Trek and Wars produced in the 20th Century will, for the most part, look as backwards to mankind as 30's-era Buck Rogers looks to us now. (This point is discussed further here.)
Finally, while in a perfect world what appeared on the screen would precisely duplicate the exact way the producers and directors wanted things to look, the perils of Hollywood . . . finite budgets, technological limitations, and simple lack of time . . . mean that things simply won't look that way. Thus we have to maintain a rational standard of how closely to analyze the evidence. For example, one can hardly start claiming that so-and-so is a shapeshifter because you can see that a stunt double filled in during an action scene. Even the CGI wizardry of ILM, when applied to covering up a stunt double's face with that of Palpatine in Episode III, couldn't quite make things look right.
(However, the rational standard maintained on this website is far stricter than most, though handled on a case-by-case basis depending on the context. As a general rule we are more lenient toward older special visual effects when they have difficulty with realistic depictions of certain things, and less lenient toward newer effects or certain errors that occur on the set (such as Kirk's phaser falling off of his belt in "Space Seed"[TOS]).)
Finally, in cases where a scenario is required, the characters and governments are assumed to behave in a manner consistent with their portrayal in the films and episodes. This means that the Federation won't go resurrecting Bruce Lee to make über-redshirts, and the Empire cannot land hordes of Jedi Masters (or worse yet, Yoda clones) on Earth. Similarly, it is assumed that the two sides will not go grabbing each other's technology and duplicating it, so that you cannot expect to see Starfleet officers carrying lightsabers, or Galaxy class phaser strips and warp engines on a Star Destroyer. Also, arguments like "the good guys always win" are not allowed, and the argument "that was a long, long time ago, so they're all dead/super-advanced" won't work, either.
Got it? Good.
Before we can begin comparing the two universes, it is helpful to know just what is real within those universes. The Star Trek and Star Wars properties are such licensing phenomena that there is an incredible mass of text, footage, pictures, games, toys, and so on that carry their names. Do we have to know about all of it to get the whole picture of each universe? Not at all. CBS Corp. and Lucasfilm have both defined 'canon policies'. These policies dictate what is and what is not part of the official story and what constitutes official fact (i.e. the canon).
The act of defining a canon policy has a long history. Scholars believe that ancient Jewish texts were collected into the Torah, and of course the modern Christian Bibles of various sects had their list of books finalized by councils and groups. These didn't always agree, of course, which is why a Catholic Bible contains books that the King James Version does not. In acknowledged fiction, canon policies have been selected or stumbled upon as well. A group of Sir Arthur Conan Doyle fans determined the most often-referenced listing of canon Holmes novels, one of the more explicit uses of the idea.
The above examples, though, are fan-based canon policies . . . that is, the original artist(s) or copyright holders are not the ones dictating what is official, but instead a group of fans. Such fan-based canon policies are fine in situations where no artist-based or owner-based policy exists, but for our purposes an objective standard is required . . . in our case, one which comes from the artists and owners. That said, an explicit use of the term is not required for their to be a canon policy, and indeed canon policies do not require any sort of rigidly formalized codification.
For instance, Arthur C. Clarke discussed the concept of canon in the 2001 universe in the valediction of the fourth novel 3001: The Final Odyssey. He says:
Obviously there is no way in which a series of four science fiction novels, written over a period of more than thirty years of the most breathtaking developments in technology (especially in space exploration) and politics could be mutually consistent. As I wrote in the introduction to 2061, "Just as 2010: Odyssey Two was not a direct sequel to 2001: A Space Odyssey, so this book is not a linear sequel to 2010. They must all be considered as variations on the same theme, involving many of the same characters and situations, but not necessarily happening in the same universe." If you want a good analogy from another medium, listen to what Rachmaninoff and Andrew Lloyd Webber did to the same handful of notes by Paganini.
So this Final Odyssey has discarded many of the elements of its precursors, but developed others -- and I hope more important ones -- in much greater detail. And if any readers of the earlier books feel disoriented by such transmutations, I hope I can dissuade them from sending me angry letters of denunciation by adapting one of the more endearing remarks of a certain U.S. President: "It's fiction, stupid!"
Here, then, we have an instance of a series of books whose internal continuity is largely disavowed, primarily on the basis of some 30 years of production (during which time, most notably in the political sphere, the Soviet Union was dismantled, affecting much of the plot of 2010). That said, it is possible for a fan to do the mental continuity fixes necessary to maintain a single cohesive 2001 universe. In broad strokes, then, it is possible to maintain that the 2001 universe is just one universe, and not four as Clarke suggests. However, because Clarke has suggested four separate universes, any analysis of the 2001 canon would have to take that into account.
In the case of Star Trek and Star Wars, the producers have generally tried to work hard to maintain an internal consistency between episodes. In both cases, the filmed live-action material is the absolute canon, and is considered to be one cohesive whole.
This means that Star Trek has five complete series worth of
along with ten motion pictures. Paramount and CBS Corp. have also
maintained that the Star Trek novels of Jeri Taylor are
considered canon. And that is all.
The JJ Abrams film series that began in 2009 is not a part of the same
universe, and even when it purports to show some "original" details
(e.g. the Kelvin, or the destruction of Romulus), it in fact does not.
Star Wars canon is a little different. The movies are absolute canon, but the scripts and novelisations of the movies are also considered a lesser part of the canon. Also considered to a very limited and minor degree are the Star Wars radio plays broadcast on National Public Radio. And that is all. The Expanded Universe is, as per Lucas, part of a "parallel universe", with a separate history and a divergent future from what is seen in his films. The best example of this is that Lucas considers Boba Fett to have died in Return of the Jedi, but allows his novel editors at Lucas Licensing to continue to write stories about a living Boba post-RoTJ.
It should come as little surprise that the canon policies are among the most hotly-contested parts of the Vs. Debate. Modern U.S. presidential candidate debates require weeks of negotiation prior to the hour-long debate, and even in well-structured 'debates' such as legal trials the discovery phase -- with various motions and arguments regarding what evidence is acceptable -- often lasts far longer than the trial itself.
In the case of the Vs. Debate, the early days of it on Usenet saw numerous battles on the issue of canon. Most frequently, disputes revolved around whether the various technical manuals, RPG guides, novels, and so on should be considered. Via erroneous claims that Lucas personally oversaw and authorized EU material and other similar inaccuracies, the EU material was allowed in the newly-formed alt.startrek.vs.starwars group, and via their numerical majority the pro-Wars side encapsulated this into the ASVS rules. A post from 1998 is quite telling on the matter:
"Okay, okay, use the books. I just hate Kevin J. Anderson's Jedi Academy trilogy. I got nothing against the Sun Crusher or anything, and that will likely be the only thing used in the arguments on here."
Of course, that person was terribly mistaken. The EU has been a source of much confusion in Vs. Debates and continues to be a strong source of Star Wars myths. Fortunately, instead of simply saying that the EU was to be accepted in perpetuity, the ASVS group chose to phrase the rules as requiring that the canon policy of "the respective owners" be followed. By tying themselves to that objective standard, they shot themselves in the foot . . . neither Trek books nor Wars books are valid sources of information, and they never were.
Objectively speaking, the fact is, was, and remains that the EU is no more a part of the story of the Star Wars films than the Star Trek novels are for Trek films. (And for the purposes of a tech discussion it's worth noting that the EU doesn't even try to maintain anything other than internal EU storyline consistency (and subservience to the film stories) per its makers, as can be seen by comparing some of the older EU tech information to the 'one-upsmanship'-based tech inflation of more modern EU material.)
As a result, sad as it is to say, thousands and thousands of posts and years and years of effort on the Vs. Debate as seen at ASVS are largely meaningless. Many of the Star Wars inflationist ASVS old-timers reject this conclusion on subjective grounds, however, and thus there is a schism between their Star Wars and the real thing, and between their views and mine.
If you've heard something different about the canon policies of either universe (and you probably have), you might be confused. If so, more details can be found at CanonWars.com.
Or, you can head on to the Overview.
Incidentally, a surprising amount of scholarly work has been done on sci-fi fans and their respective canons. Henry Jenkins has a work entitled Textual Poachers which touches on the topic. A stimulating (if somewhat pompously verbose) interview appears here. See also this interview with Will Brooker, author of a book on Star Wars fans with a section dedicated to the question.