You are not going to see a large improvement in F-22's ground attack ability. It was first designed "not a pound for air-to-ground" as the F-15 designers used to say. When the Soviets imploded, they needed to add air-to-ground ability to the F-22 to justify it. However, the problem is that its internal bays are just too small. It can only carry two specially designed 1000lb bombs, and that just is not enough for much. Besides, there are still big problems with the moving nozles on the thing. We haven't seen the end of the price increases with that beast. The AF should have picked the F-23.
The X-35 is a lot better. It can carry 2 2000lb weapons internally, and way more outside if it needs to. And with up to 4 internal A2A missiles, stealth, and longer range than the F-16, it is a pretty good in the intercepter role as well. A stealthy plane carrying good missiles combined with Japan's AWACs aircraft are going to beat non-stealth world-class dogfighters every time.
(By the way, I don't think the X-35 will be called the F-35. The X and F numbers don't match up anymore. It will probably be the F-25.)