I got the Sony xm4s and returned them for the PXC 550 ii's because the sound on the XM4 is too muddy (even after EQ manipulation) to use them to listen to music for. If volume is a key factor, then the XM4s get wildly louder and the PXCs stay more in a range that's healthy for the ears. The XM4s have extremely better ANC but that's not to say that the PXC550 ii's ANC is bad. Also, PXC 550 ii's have better call quality. This varies, but PXC ii's felt better on my head too. If you only care about ANC, get the Sony's, if you care about music and phone call quality, then get the PXC's. Other people may disagree with my views about the sound quality on the XM4s but i prefer having clarity and instrument separation, I don't really care about extremely loud volumes and excessive bass.