I look at this more from a comics point of view, in which case a lot of it's to do with taste. DC invented the modern day idea of the superhero and as such still has a very classical view. Supes, Batman, Wonder Woman, the Green Lanterns are all pretty otherwordly characters that often seem two-dimensional, though their stories also tend to take place on a bigger scale. Marvel's characters are all post-60's and most either started as youngsters or have a very 60's sensibility so there's more wisecracking. I think their universe tends to be integrated better too in terms of crossovers and world building.
For what it's worth I voted for both, since I generally read both, but most of my favourite mainstream characters - Dardevil, Punisher, Spider-Man - are Marvel. I stopped reading at the whole Secret Wars debacle but prior to that they had a lot of really good books out - Mark Waid's Daredevil, Matt Fraction's Hawkeye and the Gillen/McKelvie Young Avengers were all top notch. Historically, Frank Miller's run on Daredevil and Chris Claremont's on Uncanny X-Men are probably the two best commercial comics runs in history. If you have any interest in the characters they're essential reading. Having said that, Brian Michael Bendis is their top writer and he's awful. Snyder, Straczynski, Simone and Johns have all done very good and occasionally great work at DC in the past few years but to be honest, Image has had the best books for a while now.
As for other media, it's hard to argue against Marvel for cinema - GOTG, Deadpool and the X-Men, Avengers and Civil War films collectively outdo the Nolan/Burton Batman flicks, and everything else DC has done has been terrible. In terms of animated output. in Batman the Animated Series and Justice League the DC Animated Universe has arguably two of the greatest cartoon shows ever made, plus Teen Titans, Young Justice, Superman: The Animated Series are all very good. The X-Men cartoon was great to begin with but fell off quite sharply and I never liked the Spider-man animated version much.