Nagato has more kills.
Nagato killed Hanzo whereas 4th Hokage would lose.
Nagato only lost to Naruto via talk-no-jutsu.
Nagato himself as a kid killed 2 ninjas in a instant.
He has the six paths of pain
He defeated Jiraiya, Kakashi and alot of others during the pain vs Naruto fight
His teamwork is also great, him and Konan have good minds and know how to plan stuff out.
Nagato has more of a chance than winning EVEN though 4th hokage is the yellow flash. A simple shinra tensei will knock the 4th Hokage away instantly.