Ramin 123 said:As someone who own(s)/(owned) both it comes down to this. If you like to be really technically brilliant and have to know everyone move in the book to win a game go for Marvel vs Capcom 3 (MvC3 for short). But if you want a more relaxed arcade-like fighting game that's accessible to those of us who are not gifted with encyclopaedic knowledge of the moves list go for MK.
I couldn't stand MvC3, I found it was impossible to gauge what the enemy would do and this whole tag-team stuff could have you destroyed without you even knowing what happened. If it's one thing I can say about MvC3, when you eventually do get into a game (the online waiting is rivalling that of Gears 2 match-making) the online connection is a lot better than MK. MK servers are crap, I was playing against a friend of mine who lives 3 miles away and it was like at least 3/4 of a second lag; that's really bad for a fighting game.
Simply put if you want something more difficult go for MvC3 or if you want something more accessible albeit more stupid, go for MK.
P.S. Some might say I've put a bit too much detail into this, but I think it's going to serve your question a lot better.
MvC3 was seriously blamed for being too easy fyi...
People aren't gifted with that knowledge, the holy spirit of Christ doesn't bestow it upon us. We just practice a whole lot lol.