who scales better?

Jax. Irelia's true damage falls off lategame so does her heal. Jax's kit doesn't.

Jax. Jax's overall synergy with items is better than Irelia's. Jax's core function of countering hypercarries also makes him a monster come late game by default, as that kind of flips a scaling game on it's head when he pulverizes the champions designed to scale the best.

Jax is probably the hardest scaling champ in the game. Look at a graph of his winrate. It's how a hypercarry's should look.

There are very few champions who can match Jax's scaling. Irelia is not one of them.

irelia doesnt have any lategame scalings xD And jax is one of the biggest lategame duellists :D

Irelia scales into the mid game, Jax into the late game.

Irelia's late game is much better after the buffs to Trinity Force, but Jax's is still better. He will bomp her skull in 1v1 and his team fighting is arguably better as well. AOE stun > single target stun.