Answer:
Dc came first, and have really epic heroes, where Marvel has some of the cooler villians, but Hero wise, Dc has the better heroes. And they're comic have a lot less filler as appose to Marvel.
______________________________________________________________
Marvel characters are complex and realistic (in general), whereas DC characters are (generally) pretty much flawless. Compare Iron Man to Batman, for example, or Thor to Superman- Iron man and Thor are almost infinitely better written.