Better champion jax or nasus

they fill different roles entirely, you can't really compare them that well.

In terms of team fights, I feel nasus is 10x more effective. He also presents a massive splitpushing presence in the mid and late-game.

Jax, on the other hand, is a big threat to anyone caught out of position. In a 1v1 duel, Jax is likely to take it early. Once Nasus hits some decent CDR and a couple hundred stacks, he's going to outsustain Jax infinitely matched up item for item. Nasus is also a lot easier on mana (20mana Q for 500+ damage every 2.4 seconds)