Is there a difference? Yes. But if you're only printing 13x19 and smaller then you will rarely (if ever) see the difference.
DxOMark - Compare cameras side by side
The big advantages of the K-5IIs over the K-01 are AF speed, a nice optical TTL viewfinder and better ergonomics.
However, if you're "purely" talking about image quality for 13x19 and smaller prints the massive price difference between the K-01 and K-5IIs probably isn't worth it.
On a personal note, I've found the detail coming out of the K-01 to be nothing less than extraordinary for a 16mp camera.