Together they should win after a long battle. Their just too hard to kill and have many tricks up their sleeve for Pain to deal with. The only way i see Pain winning is if he pulls out the Gedo Mazo.
Pain should take this with mid-difficulty. To be quite honest, this fight isn't any different from when he fought SM Naruto and KM Naruto.
Rather, Pain should take this if he decides that Chibaku Tensei is necessary. Other than that, I can see him Shinra Tensei'ing Oral and Kabuto around for awhile until they realize there's a five second interval.
Should it be all paths of pain, I am going with pain on this one. Three was more than enough for Jiraiyah who won only due to him letting his guard down so three would be able to take Orochimaru down. The rest should handle Kabuto with high difficulty until Orochimaru is defeated.
I seriously don't see why Orochimaru and Kabuto would win this match.
Pein is being HIGHLY UNDERESTIMATED if that's the case... if anything, Orochimaru isn't a threat to Pein without prep, as the same goes for Kabuto despite his Sage Mode.
You're talking to a guy who destroyed the Hidden Leaf in one day, defeated SM Naruto with mild difficulty, and lost on purpose despite obviously having the power to take down Naruto and even the KYUUBI.
As I said before, Pein takes this with mild-difficulty just because of Kabuto.