Megaman help?

What's the difference?

I dont think there is a difference. In japan they call megaman rockman which explains the bottom picture.

No difference at all, save for voice actors. Regardless, I'd go with Rockman because Japanese people tend to VA better overall than American VAs for video games. Exceptions include FFX and I guess Dragon Quest VIII.

Pick Megaman X4 if you want X to sound like a little girl.