Forgive me for not reading EVERYTHING in the thread, but dare I bring up the, "It's a movie and it looked cool to the director" logic?
Of course that could be the reason in the real world. But we don't care about the real world reason, we want an In Universe reason.
Xyex, you right when you bring up the fact that Goku wasn't as scared to fight Janemba - but to say that "Jenemba = Stronger than Base Gogeta otherwise he wouldn't have transformed into SSJ and would have just kicked his ass in base" is just wrong. There's no logic there. SSj Vegeta mopped the floor with android 19. Did Vegeta have to be SSj to do that? We don't know.
I can say, with 99.9% certainty, that yes, Vegeta
had to be an SSJ for that fight. The energy 19 stole wasn't that significant (no panting from Vegeta, no signs that it was even enough to really bother him) and yet he knew from fighting 19 that the energy he'd lost put him weaker than 20. But, that's for another topic so...
(And, again, who are Super Buu 1 2 and 3?)
Super Buu = Evil Buu + Fat Buu
Super Buu 1.5 = Super Buu + Piccolo + Goten + Trunks
Super Buu 2 = Super Buu + Piccolo + Gotenks
Super Buu 3 = Super Buu + Piccolo + Goten + Trunks + Gohan
You keep saying that. But you, again, are not taking the word 'complete' the right way. The difference between dance fusion and potara fusion is like the difference between renting a movie and buying a movie. Buying it is 'more complete' because it stays around longer, but while it's around in either case there's no difference.
XD You're the one not taking the word complete correctly. I've NEVER heard complete even remotely refrenced in that situation. A complete fusion would mean that the bonds of the two being fused are sealed making them 1 complete person with no degradation to the fusion. The dance isn't this powerful, the bonds aren't this strong, and after a time they break down and result in a de-fusion. It's just that simple.
So, no character ever used a powered up form beyond what he needed to? No one? Not even, say, Vegetto? You said he was clearly stronger than Super Buu 3 in his base form, but Vegetto still transformed into a Super Saiyan.
I
knew you'd bring this up.

Vegetto didn't transform because he
needed the power to win, he transfromed so that Buu would see absorbing him as the only means to win.
Well...Elder Kaioshin actually said that about the possible fusion of Goku and Gohan. The fact that it was Vegeta changes the truth of that statement.
Oh ya, he does... but doesn't he say something later about Goku and Vegeta making an even stronger fusion? Or is my memory just going wonky?
Originally, Vegetto transforms right away, and I don't believe he would have done so without having good reason to.
Freeing the others is pretty much the only reason, IMO, that he bothered. He so seriously outclassed him as an SSJ I find it hard to swallow that he wasn't at least even with him in base.
And even in the Anime, Boo tells Base Vegetto that "Despite your great strength, you are no match for my full power!" Vegetto transforms after this. So I guess he agreed with Boo.
That was his way of going "Nope, I don't think so." to show Buu that his only option left was to absorb him.
However, I do agree with the rest of what you said!
You know, the more we agree with each other, the more scared I get.
The fact that the fusions start off transformed already(sometimes.) always bugged me, especially in Movie 13. How the heck can Goten and Trunks be base form, fuse, and turn out SSJ3?
Transform upon full merger. I might be remembering the scene wrong, but I think I saw his hair growing while he was still glowing. It's like *boom, fusion formed* *boom, transformed* all in about .1 seconds.
But, I think, we've already established that the reason he appeared as a Super Saiyan immediatly upon the fusion is because he wanted to.
Of course he wanted to. He need to so that he'd have the power to beat Jenemba.
When Vegeto turned SSJ, he had sparks around his aura. Does this mean he quickly powered up to SSJ2?
Actually, it does, and he did.
._.
No. Now, again, this could be my memory going wonky... (Duo would know better than I) but I believe that Piccolo exhibited sparks around his aura after merging with Kami... so I guess that makes him an SSJ2 as well? The sparks / lightning to the auras is to denote power, not stage. It's become associated with SSJ2 because that's where it first appeared and, aside from SSJ3, where it is most prevelant.