Same sound quality and both close headsets. Both are bad durability. I have 7H and after playing 3 hours not enjoyable. If you deciding to buy long life headset I recommend you Sennheiser PC 350(close) or PC 330.
steelseries headsets (aside from siberia) seem to break within a year or two. it's always the wires or some techical difficulties (this was the experience with me, and i'm the kind that takes good care of my stuff). i don't think the quality is whooping either. if you have the budget for it, try sennheiser pc 350 (closed) or pc 360 (open)