But all of those are GPUs, and all have totally different performance, just like if you compare completely different dedicated GPUs.
iGPU is incredibly broad, the one on the Core 2 Duo is going to be significantly worse than one with the new Iris technology or whatnot.
Not so well , if you play any game at 3xIR[1080p] both AMD APU and latest Intel CPU will take performance hit
Sweet spot for APU : 2x or 2.5xIR
Btw , on pcsx2 , apu and intel igpu perform even worse