Baradok
High Matriarch, 7th house
well for the case of whats more realistic take in the sense these are comic books lol but yes the reason JLA isnt as realistic is because the heroes in that are ment to be seperated into their own comic books making them solo and the only hero. When you put them together you put several super powers together with years of expirience
When it comes to experience for X-men it is limited to maybe 4 characters and proffesor X is the only main character with Experience....
now the point you make Mav with Flash being so fast there are more then one X-man and more then one JLA member so he cant do everything... and your point about him finding all of the JLA's weaknesses would only weaken his own team... yes Wolverines arrgoance and thick skull would prolly slow the team down and yes Thor knocked out storm with one blow.. but remember shes a girl none the less.. her body size cant sustain a blow like that her powers are transmitted through the brain not the fist
i would have to say the fight would be very close and most characters would die in the fight leaving the winning team with few remaining members... which brings the down side, Superman has come back from the dead several times whats stopping him from doing it again, there are a lot of things that coul turn the batle in a flash of an eye