I'm going with Star Wars. Star Wars is an actual universe that contains at least 1000s of years of history. The Avengers refers to a specific group of super-humans working together for a certain reason. Marvel Universe as a whole may be better and even certain Avengers. I've read the original Avengers comics in the last year or two and really enjoyed them. The Scarlet Witch and Vision may be even more important to me than the actual group of Avengers. The Avengers have also been corrupt at times(like under Norman Osborn), leading to problems with the true heroes. The movie Avengers are a good line-up, but the ambiguity of this question could just pertain to the events of the Avengers in and out of the comics. When certain members are busy, their stories are only alluded to. Star Wars: The Old Republic is just another addition to Star Wars as an example of depth not necessarily thought about.
I believe Star Wars and Marvel have had a cross-over as well. In that separate universe, it still contained all the Marvel heroes leaving only the specific actions of the Avengers to fight against essentially the members of their group, everyone in their universe, and all Star Wars events/times.
If it were Marvel vs. Star Wars, excluding the cross-over would be more reasonable. Wording is really what keeps the Avengers down. Avengers only have 1 live action movie (unless Captain America: The First Avenger counts (he's not the first Avenger alive even in the Marvel movie universe)), vs. the six live action Star Wars movies. Avengers would make up a lot of ground on the animated front, but still Star Wars has its own series(plural).
So I give this battle to Star Wars. I don't really see the purpose of comparing them as they are different things. It's not like people absolutely have to choose one or the other irl. Someone holding a light-saber and wielding Captain America's shield at the same time has probably already happened. Marvel vs. DC would be more of a direct comparison (though neither is done writing). Star Wars does have far less interesting protagonists and antagonists imo.