Both at full power
Aizen can become full form if he is angry, but his full form is featless..
10 minute prep
Final Getsuga Ichigo's power was not even enough to destroy soul society, let alone with just it's spiritual pressure and effect even the high level captains who were far away like Yamamoto's bankai is doing, on top of that Aizen has to make a being for the soul purpose of getting rid of the flames from just his shikai. Yamamoto would take out Aizen in seconds, he really can't hurt Yama and he can get out of all his hado's easily, while all Yama has to do is get close to win. Not to mention Aizen has no idea what Yama's bankai is so that's another disadvantage. That said, Yama wins in a stomp.
@eddz99: He can't research something he has no knowledge of, the best he can do is make another Wonderweiss or something. Also, he already had prep the first time, the prep being him being in Soul Society for decades, keep in mind that the whole plan to take on Yamamoto most likely took a LOT more than the 10 minuets of prep you gave him lol. I never said Ichigo killed him but it was enough to keep him down, Yamamoto's bankai is vastly stronger so I see no reason to believe he would not take him down easier. Yamamoto starts out in bankai as well. Plus in final form doesn't Aizen lost his shikai ability? I just really don't think Aizen has what it takes at this point. Yamamoto was already giving him trouble without his shikai and Aizen thought he was a threat with Shikai alone even saying that in a fair fight he would win. So I still side with Yamamoto.
@DBZ_universe: Yeah, the only reason Aizen was at such an advantage against all the Captains was because most of them were already under his Zanpakuto's genjutsu.
Yamamoto's still easily the most powerful Captain by far as even in shikai he was taking on 2 of the most powerful captains with what looked like little difficulty. 10 mins prep won't help Aizen much at all.
@ohgodwhy: That's true.... 10 mins wont do much for Aizen... unless Yamamoto is under his hypnosis...
@taichokage: maybe not as strong in sheer power, but I think Aizen's Bankai would be more hax though considering how broken his Shikai is... his bankai would worst.
Im not sure about that actually. The hougyoku left him, only leaving him immortal. And it is said that when a zanpakutou is destroyed yet the user remains alive, the zanpakutou will reform. I have even wondered if he was able to use it before he was imprisoned. If he recovered his zanpakutou, he could have tricked everyone into believing that he was imprisoned while the real Aizen is at large again. Basically he could have repeated the same plot again and nobody would know better. I even have a strong belief that he is the one who rescued Urahara. Just look at good pictures of Kyouka Suigetsu and the sword at Urahara's neck. They have the same unique color theme! Of course I might be very wrong, but one way or another I do believe we will see Aizen again and probably sooner than we think.
OMG!!! that theory you just made is EPIC!! I want to see that happening!!
and tricking the console and him trolling behind the scenes would be awesome! lol
Remember when Yama-jii battled Aizen? He didn't used his bankai because he knew that Aizen would just troll him, that's why he used "Ennetsu Jigoku" for a huge AoE, so that even Aizen can't escape. But Aizen came prepared with Wonderweiss.
Assuming Perfect Aizen still has Kyoka Suigetsu and decided to use it, he has a verry high chance of winning.