Minato probably wins. He can learn Sage Mode so his chakra reserves are easily far larger than Kakashi's, so in terms of clones he'd outnumber him. Tobirama said that Minato's Shunshin is even faster than his, meaning Tobirama himself is faster than the rest of the Hokage...including Hashirama who was matching Madara in speed and otherwise has good speed feats of his own. Madara caught SM Naruto off guard.
-Rasengan>Raikiri.
-Minato can sense chakra so we can forget about surprise attacks.
-Boss summons are also another issue for Kakashi, not really needed though.
-Minato's reflexes>>>Kakashi's.
-Minato's natural speed>>>Kakashi's.
-Clones.
Kakashi's best shot is to have him defeat a Raiton Clone, paralyze him and then take him out then, but if Minato has a clone out when this occurs the strategy fails.