Who will win between the two?
1. "Emperor Joker was a Multiverseal threat while Mad Jim Jasper was an threat."
2. "Joker myx's powers are , to manipulate"
1. Bullshit. Anyone making the "omniverse/omniversal" claim, about anyone, or about the universes by any specific company, doesn't know what the word(omniverse) actually means.
2. Double bullshit. First of all, Mxy's powers are not limitless. Second, Jim Jaspers did not need "matter" he needed "reality" in order for his "Reality Warping" powers to work, he was made powerless by being taken outside of reality.
That said, based on feats, Emperor Joker takes it. On paper, it would likely be a stalemate.