Personally I think Bach is stronger than Aizen, it doesn't make sense to introduce a main villain who is weaker than the last. It does show that Bach was manipulated by KS or something from Aizen, but perhaps it is a testament to Bach that he was only effected that much (a few minutes I believe) he also seemed unconcerned with Aizen after that, kinda as if he was no longer important. Bach is probably stronger if not currently, then when he gets all his power back from the sternritters.
This brings something up though, why did Aizen manipulate bach? What was his goal there? I would say it is likely that Aizen comes back in some way, maybe just to see the soul king at least.
This brings something up though, why did Aizen manipulate bach? What was his goal there? I would say it is likely that Aizen comes back in some way, maybe just to see the soul king at least.