[Richbot]

I have a set of 275/35-18 Contis ExtremeContact sporst on my 18x10 Bimmerworld wheels, and a set of 275/30-19 PS4S on my square set of 9.5 OEM 220M's. I'm driving on the Michelins right now and they're great tires, but the ultimate grip is not a big enuogh difference to justify the price difference - the PS4S do wear significantly better, but if you're staggered your'e going to be replacing tires relatively often due to camber/toe wear, particularly up front. The contis are quieter on my car - this is my second set of them in a couple different sizes.

I'd use the Conti, especially if you plan to track the car. The conti is an amazingly capable and consistent track tire for a "true street" summer tire, slower than the PS4S over 1-2 laps, but doesn't fall off a cliff and is friendly and predictable and good in the rain down to the wear bars.

I did the 275/295 split with the old Conti DW and absolutely hated it. The ECS is a totally different tire, it's a blast. We also put them on our E63 when the oem garbage fire tires wore out, and the grip is almost too good to be fun.

Another difference - the PS4S is an edgier tire at the limit. If you are looking for friendlier limit behavior than you had on your square Michelin setup, the Conti is your droid. The 285 Michelin on a 10.5 is not going to behave significantly different from a 275 on a 10, you might have a little less oversteer but the limit behavior will be the same - a little edgy/snappy.