Setting Grand Kai's planet.
Super Buu easily better than Vegeta and Goku. Gohan easily better than them all. However Buu absorbs a person, we don't know how much power it increases. With the fusion, it's easily above double the amount. Putting together full power Goten and Trunks' you won't get more than Goku at ssj2 level. When fusing their power seems to be closer, and when both at ssj3 Gotenks would appear to be more. That would lead me to believe if you fused Goku and possible Goten, that would be enough to defeat Super Buu. Who knowns maybe even enough to defeat Mystic Gohan. Vegeta would obviously outclass the kids. So if you put two power levels of Goku and Vegeta together I think you could get more than Buuhan based on the massive increase of Goten and Trunks' fusion. I remember Grand Elder Kai saying it would increase more since Goku and Vegeta were rivals. I don't remember if that was filler/dub-error whatever. If it's true, then it'll power it more.
I'm also in the department of Porta Earrings having a much powerful increase than Fusion Dance.
Buuhan would win, 2 reasons why 1.fusion is weaker then the potara fusion been stated by the kai(so in my opinion Gogeta could be equal or alil bit stronger than Buuhan) 2.The 30min time limite, and Buuhan knows of this weakness because of absorbing gotenks so if Gogeta is stronger than Buuhan,then Buuhan will use the knowledge he aquired from absorbing Gohan and piccolo to hang on till 30min pass..
@eddz99: When did they hit him just by looking at him?
Made shenron fly
I know that now. I was thinking of when Shenron was flying towards Gogeta and Gogeta punched him so fast that it seemed like he never touched him.
At 1:19 of the video is what i'm talking about.