What are the major character differences between Marvel & DC?
I think that, as a general rule, DC’s characters are more fanciful, and Marvel’s characters are more grounded. So typically, I like it best when DC plays to the strengths of their characters, rather than trying to reinvent them in a more Marvel-style way, or make them seem edgier or more violent or what have you. This is also why my answer to any question about swapping characters between universes is the same: with the best of these characters, when you move them to the other universe, you lose some ineffable part of what makes them what they are.