No question. Here's "classic" Akatsuki:
1) Pain (Rinnegan 6 bodies, a dozen summons, shared field of vision, ability to resurrect dead teammates)
2) Konan (Can fly, can use lots of projectiles)
3) Sasori (100 puppets, after you get passed the outer puppet shell and the second kazekage with his iron sand. Also, lots of poison)
4) Deidara (Can fly on his big bird thing. Can create hundreds of bombs)
5) Hidan (Immortal)
6) Kakuzu (4 hearts with 4 different elementals, ability to split them out into 4 separate creatures for distributed attack)
7) Itachi (world expert at Genjutsu. MS with perfected Susanoo, Amaterasu, the best Tsukuyomi)
8) Kisame (huge amount of chakra, ability to absorb chakra, expert with Samehada)
9) Madara (space/time techniques, powerful sharingan, Izanagi in a pinch)
Even if you give Kisame over to the other side, it's not a fair fight. Akatsuki wins without even having to try hard.