>>13609023This.
Mewtwo asks if he's just a copy, but he's corrected when the science dude tells him he's greater than Mew, and that his psychic power exceeds that of an actual Mew. The fight is probably the closest we'll ever get to knowing, since there was no winner it can be assumed that they are of equal strength.
However, the Mewtwo from Unova is a total pussybitch.