Jayce, 'cause Ryze's ratios got nerfed to shit.
It used to be like:
Ryze has shit early and Jayce usually wins lane hard against him
Ryze outscales Jayce in late if he manages to survive the hellish lane, but usually the Jayce will snowball harder than Ryze.
Now it's like:
Ryze still has a shit early, same situation as before
Jayce goes reasonably even with Ryze even if not snowballing, completely shits on Ryze if he is.
Ryze will definitely rush armor though, so it really depends on who either of them are fighting. In terms of true damage output, I'd say Jayce beats Ryze.