I'd say Minato...
- Minato is known for his ultra speed (yellow flash), which is why he was the fastest shinoby when he was alive (said by Raikage himself).
- He is also very clever and very observant, so he can figure out the 5-sec break betwen shinra tenseis.
- If Minato places a tag on Nagato, Nagato looses.
- If Nagato uses Universal Pull, Minato just teleports to other tags around the battlefield.
The only way I can see for Nagato to defeat Minato is that gravitational orb, but it just takes too long to create: meaning, Minato will strike then and even if he doesn't kill, he can place a tag and come back any tume he wants.