If the circumstances for both of them are optimum (Vegito at SSJ2, at full health and with a tail and Superman prime fully charged with solar energy, wearing his solar energy collecting suit) Vegito would probably win from Superman prime.
vegito
super vegito
Depends on the version of superman you are using.
superman and spiderman
Vegito even in his Normal state.
Super Vegito
super vegito
Vegito. He could just blow up the universe by snapping his fingers(tht includes supermans source of power the yellow suns) and then teleport to heaven(thts assuming the explosion would even hurt him) with instant transmission and be done with it.
Vegito would win. Majuub would easily lose and so would Gokule. Gotenks is strong, but not as strong as Gogeta or Vegito. Vegito would defeat Gogeta simply because Gogetas fusion would time out.
Superman would win.
now the obvious answer to this question is superman. Every one knows that optus prime is helpless to super man. So the answer is superman
Vegito is alot stronger than Gogita. I know, Elder Kai said that Vegito is stronger because it last forever & has no time limit.