To see if one is better than the other will really take more than looking or measuring diameter. What materials are they? What is the ring side clearance? Is it consistant? Are the edges left sharp from machining? Where was material removed from to lighten them? How thick are the domes? How well are the pistons in terms of measurements matched? I like the KBs in forged or hypers. I've used Ross a couple times in kits and they were fine too. but I think the KBs have a better quality machining in terms of identical parts and tighter tolerances, even if they leave the edges sharper than what I like. (yes, I end up dressing the corners anyway...) The reason top name pistosn cost more is more than appearance. It's much tighter tolerances, better material, and more attention to detail.