I can say that I significantly prefer DC's universe. When I think of superheroes I think of vibrant, noble characters in completely out-of-this-world kind of adventures, and that's exactly DC's style in terms of art and story direction. I don't hate Marvel or anything, but to me their Universe is too dark and severe. I'm also not a big fan of how they've tried to turn so many of their characters into anti-heroes (they were terrible with this during the 90s). I still like the Avengers, Doctor Strange and that, though. While I haven't read it just yet, I'm very interested in reading Annihilation, and then Nova's ongoing series. I'll get around to those before the end of the year, as they sound awesome.

Now, if you talk about comics in general, I'm not quite as DC-loyal. The only things I regularly buy from DC are Geoff Johns' Green Lantern trades and Batman books, while I'm currently getting into Marvel's Cosmic characters along with buying a bunch of their fantasy comics. Overall I'm about middle ground product-wise, favoring DC a bit.