I like both but why do people try to compare the two so often? Other then taking place in space and having "Star" in their title, they are nothing alike.
Star Trek is hard sci-fi, Star Wars is fantasy that happens to have space ships.
I love both but if I had to choose, I would pick Star Trek. I would say ST is by far the most mature of the two. It's about exploration yes but at it's core it's about humanity. I have been watching Star Trek: Deep Space Nine recently and much of the show is centered around the Dominion War, what I really love about it is that they go out of their way to make sure there is more to it then fast ships and explosions. Many episodes explore the horrors of war and the writers tried hard to bring that humanity into it.
One great episode is The Siege of AR-558, it does an amazing job of showing what it's like to be in long term combat and that the psychological wounds can be just as bad if not worse then physical wounds. One of the main characters loses a leg in that battle and a couple of episodes later a whole episode is dedicated to showing that persons struggle with readjusting to the real world and of course dealing with the trauma they suffered. Actual vets worked with the show and many more applauded them for their accurate representation of PTSD. One of many great scenes from the Siege of AR-558:
[video=youtube;-D2SHNqkjbY]http://www.youtube.com/watch?v=-D2SHNqkjbY&feature=related[/video]
In another episode Captain Sisko faces the fact the Federation will probably lose the war, so what does he do? He forges evidence to get another alien race to break treaty with the Dominion and join them. This is the hero of the show people, who made a decision that may be immoral but felt he had to. Not only that but the man he worked with to forge the evidence went as far as to assassinate the senator of that alien senator in order to bring them into the war. I was impressed a show was willing to do something like that, to make you question your own morality in the face of damming odds.
[video=youtube;IPocxGUWMxM]http://www.youtube.com/watch?v=IPocxGUWMxM&feature=related[/video]
Those are just a few of the many raw and real human themes Star Trek explores and why I pick it.