Pretty interesting thread. Id like to take a stab at this and show what my opinion on who is the victor:
Minato:
-FTG being able to close the gap between the next Shinra Tensei from the last. This easily puts him in the range of taking out Deva.
-Sharp ninja mind would allow him to decipher most, if not all, of Pain's ability after a certain time. Minato's intelligence on the battlefield was noted by certain ninja in the series.
-Rasengan against Pain, if Naruto can take out Deva with a regular one then Minato should easily be able to as well. Also, Minato does not need Bunshin to create it thus making it easier for him along with Hiraishin level 2.
-Vast array of sealing techniques
-Toad Summonings.
Six Paths of Pain
-Summonings. Cerebrus Dog, Chameleon, Flying Bird etc. Powerful assists in the battle.
-Revival capabilities.
-Soul stealing capabilities, however I think this wouldnt have much use against Minato.
-Vast array of high tech, powerful weapontry.
-Absorbing chakra
-Gravitational capabilities.
-Chibaku Tensei
This battle could go many different ways as I see it. IF Minato was sharp enough, he could deduce the time frame between the main offensive(Deva) attack and take him out. However this would be unlikely, since this would not be his main focus in battle and he would have to deal with the other Pains afterwards. This is not one of my arguements but its one that could be if the scenario was put that way.
1)If Minato were to figure out the Six Paths of Pain and decipher the secret to their abilities then he would have a much higher chance of winning this. Minato and his highly intellectual mind would strategically plan out his next target until he is left with the last Pain. There are few things that could get in his way:
-Deva Pain, Shinra Tensei would smack him despite using FTG. However the recovery time for FTG would be faster than his Shinra Tensei thus allowing him to strike next first.
-If Pain were to find out the use of his Kunai in battle fast enough, he could easily have one Pain go after wherever he threw them at. However, this would take a little bit of time meaning Minato has enough time to put the FTG seal on the Pains or elsewhere.
-Summonings are a hassle, Cerebrus Dog would take multiple summonings to deal with extensively along with any other animal he could summon. Im not sure how many toads Minato has access to with summonings but I dont think he would have an easy time with just one.
-FTG seal could be placed on each of the Pain's if he could fake an attack to place them on the bodies. That would hinder their attack time to practically none, leaving almost all of them for a surprise attack.
Here Minato has an advantage and can strategically take out each Pain accordingly.
2)If Minato is unable to find out enough info on the Pains in time, then he is a sitting duck. Pain could easily find out the use of his Kunai faster than he has to figure out all six powers. That would mean that Pain is able to strategically counter this using powerful summonings to assist in covering his attacks. The tag team of six could overwhelm Minato if he is too busy trying to decipher their abilities.
-Chameleon summoning would allow Pain to slip away, easily providing hassle for Minato and his attacks.
-Preta Path is a powerful asset for Pain, as we see Minato's main form of offense is the Rasengan. Rasengan is chakra, so without it Minato would not be able to attack with his main offensive jutsu/
-Revival is key to their win, and without proper info Minato would ignore this path completely before he catches on. By then he would be out of stamina or chakra.
-Deva could use Bansho Tennin to attract all the Kunais to his body, which would spell disaster for Minato's main strategic advantage in this battle.
Conlusion: The odds of Minato learning every Path's secret in time to effectively counter the team are very slim. For one, each Path does not reveal its power until a certain time period such as the Naraka Path who is there to use the Demon God Sealing jutsu (Idr what its called) and to revive fallen Paths. Also, even though Minato is able to go hand to hand with most of the Pains, the Preta Path is his most challenging yet. Minato is not a Taijutsu specialist nor have we seen many other offensive jutsus from him other than Rasengan. With only Rasengan, Preta is able to absorb it and Minato would be left defenseless. We can't give Minato a jutsu that he hasnt shown yet in the series. That means he would be challenged to the max with this path.
If he somehow managed to learn the secrets in time, then he could have Gamabunta destroy the Preta Path or any he has trouble with. But then again, Animal Path would have his summoning on the ropes with the Cerebrus that keeps multiplying and outnumbering his toad. Seals on each of the Pain would be a good bet to use, but at some point Deva is bound to use Shinra Tensei to protect himself. This would hinder him from getting close or using Kunai since the force would blow the kunai back. Do not forget that Minato has chakra, and he is no Uzumaki. He wont outlast Nagato's chakra and eventually the tag team could pin him while hes getting weak.
So:
Minato FTG Kunai<Shinra Tensei or Bansho Tenin
FTG Seal>Most Pains aside from Deva and Preta.
Toad Summoning<Cerebrus Dog along with other animals.
Rasengan>all Pains except for Preta.
Chibaku Tensei = Disaster for Minato.
So the conclusion is that Minato is able to come toe to toe with most of the Paths hes up against. However, in the long run, he would be left with a considerable amount to deal with. There are too many things he has to be concise about, otherwise he would end up dead. Without seals around the battlefield or on the Pains, then he cannot move around for long once his secret is revealed. Despite that, the minimum amount of Rasengans he'd have to use are six. Thats alot of chakra dispelled. So my vote goes to the Six Paths of Pain. With difficulty.