Marvel for me since the characters are more relatable and flawed. DC has godlike characters that are perfect and less interesting, besides Batman of course.
Movie-wise, DC isn't looking so hot. I don't like that they're shoving in Aqua-man and Wonder Woman into Batman v Superman. It feels rushed like they're desperately trying to catch up to Marvel. The style of the movies is dark and gritty, except that also seems to mean washed out and dull in Man of Steel. Adding onto that, they try so hard for the movie to be serious constantly that it becomes a parody of itself. Serious moments, mixed with action, mixed with more serious moments, mixed with explosions, doesn't lend itself well to pacing. It comes off heavy handed and boring (just like the colour palette).
Maybe not the best image comparison, but you get the idea. Man of Steel was very grey looking.
The thing that made Nolan's Dark Knight trilogy so good was that he knew to balance it out. It was done well for a gritty and realistic take on Batman because it recognised that gritty and realistic didn't necessarily mean grey, washed out, always serious dialogue and lots of action. It knew to take breathers in places, keep a colourful palette, inject some light-hearted conversation and so on. Plus, Batman is a much more flawed character than Superman as well, so that probably helps keep him interesting. The key here is to have variety.
I like Marvel better because they've taken their time to introduce the characters (I'm looking at both Sony and Warner Bros here). With them they started the shared universe thing, and while other studios could have done it well without it feeling like a cash grab, it feels like a cash grab because they rushed into it. The Amazing Spider-Man is the perfect example, because that movie came out in 2012... So they would have worked on it before The Avengers came out. Then obviously, everyone saw what a success that was and Sony (the worst offender) managed to cram Oscorp, Electro, Green Goblin, Rhino and Sinister Six set up in the same film. The ending scene (which is a cliff hanger) with Rhino literally crammed into the last 5 minutes is a testament to the fact that:
1. The canvas is way overcrowded.
2. They obviously setting up a franchise of sequels, spin-offs and so on (which is okay, as long as you're not overly obvious about it with the cliff-hangers and all, which will piss people off).
Warner Bros has treated DC slightly the same way, although not as bad, it can't be excused. They're cramming in Wonder Woman and Aquaman when it's meant to be Batman v Superman. Batman and Superman should be the main points of focus, and I just can't see that happening if they're introducing other characters. There needs to be a clash of ideologies, not just some 10 minute superhero fight (while awesome) over some misunderstanding or whatever (not so awesome).
Marvel have taken their time, made movies which stand on their own (FYI, I watched The Avengers without seeing Captain America or Thor at the time and still understood it extremely well), have characters that feel human, light hearted stuff and even their movies don't all feel the same. Guardians of the Galaxy; a space opera. Thor; a film about mythology and so on. Captain America; ideology, war propaganda, different time period. Even the second Captain America feels entirely different from the first, due to the time period, setting and change of politics.
You wanted my honest opinion so there you have it. I still want to see what DC can do, but I'm not confident in Zack Snyder to be honest. I'll probably still watch Batman v Superman because I want to, but I'm not nearly as hyped as I am for Age of Ultron. I'm a huge Marvel fanboy. :)