This is almost as large of a can of worms as which chip company. But anyway, you'll hear gobs of people say oem, that's all nothing else. Mainly those people will have had warpage problems. Others don't like slotted because of pad wear, alot don't like drilled because of even more chance of warpage. I think if you break them in properly, you should be able to avoid warping them, but Volvo's are big, so the rotors do see some action! I did a little test on my wifes 95 855 and my 98 s70T5. I got her brembo, and I got Brembo slotted. Both PBR metal master, thank goodness, NO DUST!!! And so far so good no warping, excess wear or anything, except for a few extra bucks in the wallet, as OEM has its usual OEM price!! Oh, I avoided Zimmerman, heard one or two stories of them not being as thick or hearty. Balo..?? If Porsche likes Brembo, its good enough for me!