it's a quite dirty fight here. orochimaru's jutsus don't really have much strength to minato. rashomon, edo tensei, and all those won't really work.
but minato's got speed and rasengan but those won't do much damage to oro. minato's good with seals, but oro and jiraiya are also good with those...it's not like neji's attacks that would immidiately stop the chakra flow (even that would be broken by burst of chakra)
if orochimaru goes to final form, it's like minato fighting a smaller, weaker kyuubi...manda vs gamabunta so their summons would be off.
i would give the edge to minato, but both of them really are not the best matchup for each other. if they met, i'd expect orochimaru to easily giveup and flee, but if they fought to the death i'd say it's close.
minato, anyways.