-If Reatsu=Chakra then KS woud be just more efective against Obito
-Aizen is a kido master , and some of the kidos can one shot Obito
Aizen way faster than Obito
Any version of Aizen woud stomp Obito
If its Obito then Aizen stomp all round .
If ts juubito , than its a little diferent , but not so much , i think juubito woud be able to beat base Aizen if he doesnt get cought in KS or in some uncategorized spell or kido , even juubito woud stop at hogyoku Aizen , BFR isnt an option here , Aizen can regenerate from everything juubito shoot at him , and Aizen can "dimension hop".
Also arent "Monster" Aizen supposed to be transcendent ?
UI:. If even bankai Gin and yamamoto cant destroy him , than no one in naruto can , but he can be sealed (with tricks ) maybe , but Obito and Juubito woud loose to any version of Aizen , from hogyoku to EOS