strongest of the three sannin

[Kratos of cruxis]

I say jman is slightly stronger then oro

 

[USSJ Future Trunks]

orochimaru. poison blood, edo tensei, hydra, formation of ten thousand snakes, leech all creation, kusanagi blade.

This has been proven as he went toe to toe with oro and was holding his own even after Tsunade poisoned him in part 1.

oro had no arms and lost most of his ninjutsu as a result