if u say GH4 drums will be better than RB2 drums...do some research...
GH4 drums: ~3 drums ~2 cymbols ~"sensitive pads" - harder the hit, louder the sound
RB2 drums: ~4 drums, moveable and ajustable. ~3 cymbols, removable and ajustable. ~wireless ~"freestyle drum mode" ~ive heard of a mode that will actually TEACH you to play set. (self-taught drummer here btw)
plus, GH is just adding drums to keep up with RB. personally, i think GH is called GH for a reason.