Minato VS Orochimaru.
I like minato more than I like Orochimaru, but I will not be baised. They are both geniuses and skilled ninja
Orochimaru's mainly used techniques, or techniques that have been shown in the manga are.
*Curse Mark
*Summoning
*Oral Rebirth Technique
*Edo Tensei
*8 headed snake technique
*Rashomon
Now for minato's techniques.
*FTG technique
*Rasengan
*Space-Time barrier
*Many Space-Time jutsus
*Dead Demon Consumming seal
*Four Symbols Seal
Okay, so lets see. Lets go with Orochimaru. His Taijutsu skills are pretty weak amongst other main characters. However his skill in Ninjutsu is strong. If he manages to hit Minato with the curse Mark, Minato is done for. While in Pain, Orochi can strike the finishing blow. He can also Summon many snakes, but they are usually disposed of quickly, so against a kage such as minato, not very effective. Manda however would be a problem, therefore, Minato can summon Gama and other frogs to counter that. Edo Tensie could be problematic, all we've seen from orochi using it was the 1st and 2nd. Orochi never mastered the technique, so in this case, we cant say the summons would be as powerful as Kabuto's Edo. And if Minato does manage to land a hard hit on oro, orochi can easily use his oral rebirth. However that technique requires ALOT of Chakra, while FTG does not, oro will eventually begin to run low. The 8 headed snake technique is a very powerful technique that would destroy any summon Minato brings out.
Rashoman will easily block all attacks that Minato unleashes, how ever they arent instantaneous.
Now, Minato.
He has very good reflexes and speed on his own, so its safe to assume he has much better taijutsu than orochimaru. His FTG will pretty much counter Orochi's oral rebirth techniques by constantly appearing out of various places, he can even plant a seal on Orochimaru without oro even noticing it (If Tobi, an "Uchiha"/extremely exprienced ninja with a sharingan couldnt notice, i doubt orochi would) and can attack from anywhere at the blink of an eye, will eventually tire orochi out. If Orochi summons manda, Minato will counter with Gama, and use a Four sealing technique on Manda and seal him away into an object(scroll, etc) Rasengan will force oro into a oral rebirth, but minato is fast enough to keep up with that ans continously bombard oro with FTG. If Oro transforms into the 8 headed snake, as he attacks, Minato can use his space-time barrier and transport the attack, or the giant snake itself elsewhere and surprise attack the confsed orochi with summoning, or a sealing technique.
I would have to give it to Minato only becasue of his speed combined with his spacetime and sealing.a great combo.