Ok, off the top of my head, Trundle is better. He can have virtually the same build; is tankier; has 80% attack speed at level 5 Frozen Domain (attainable at level 9) against Jax's highest level of Relentless Assault of 84% at level 16; is as or more mobile; has what I consider a better crowd control spell; actually incurs the cooldown on his AA reset when using it on structures and gains 40 damage when using it; can arguably chase and flee better; is a better team fighter; is equally or more effective as a duelist. He can actually beat Jax, both in lane and later. Jax is not as good as he used to be - he's not a god anymore.