I go with marvel because despite some of their stupider mistakes (spider-man made a deal with the devil? wtf?) they make their characters a bit more "human" that and things make more sense continuity wise. Here's a few examples:
at one time, superman went rogue, and went on a rampage. Batman, seeing this, brought out the kryptonite to stop him, and saved humanity. However, when batman went rogue and off the deep end, Superman stopped him and won, saving humanity. WTF? if batman could stop superman before with kryptonite when superman lost his shit, why couldn't he have stopped superman in his tracks when he lost his morals? In DC, the good guy wins, the bad guy loses, no matter what.
In Marvel, wolverine went apeshit because he was possesed by an alien chick. it turns out she wasn't evil, just testing his powers and physical limits. To do that, it took almost every hero in the marvel universe to stop him, and they still failed and almost all of the ones who went up against him nearly died. Wolverine had a conscience for a reason. without such scruples, add in a healing factor and a taste for blood, and hes one tough son of a ***** to stop, in the end, he had to save himself.
Also in marvel you had some of the higher ups in the marvel universe (xavier, richard reed, tony stark, and a couple others, i forget who) decide to get rid of a large green problem by jetting him off into space, basically a "ok we dont know what to really do to stop him, lets just get rid of him" storyline. later, when they find out hes still alive, try to nuke his ass, which of course doesnt work, and ends up (to hulk) killing his wife and unborn son. He later goes against the entire marvel universe and does a shit-ton of damage before hes finally stopped.
In DC, superman has tied at least once, and come back. The infamous "death of superman" arc. In marvel, they killed off captain america and it wasn't a temporal vortex thing, wasnt a body double, no, cap died, and to my knowledge (i havent kept up with them recently) stayed dead.
Marvel characters have real world flaws. Tony stark and his alchoholism for example. Superman as far as i have seen, has no real world flaws or things to make him "human". Theres a reason batman calls him the boy scout. Now if you want a superhero with issues, yes batman makes up for that in spades...but one hero vs an entire publication of heroes with issues. i mean come on.
Sorry for the wall of text, but i figured this would be my two cents...