Yes, you will see a performance difference between all season and summer. Yes, I'm in SoCal so I know about the seasons. lol As an example, on my G35 I had michelin pilot all season I could break loose easy. Replaced with firestone summer and couldn't do it and they were more quiet by a lot. That's just my example experience.

I don't run 21s thank goodness, but it surprises me that you guys/girls to the south of us don't often consider Yokos,Bridgestone, or Toyo.They're big up here in Quebec. I run Bridgestone summers and Yoko winters.Wonderful products.

I definitely wouldn't have ever screwed around with the tires on my SL500 but the performance needs and my expectation as a driver of a rear wheel sports car versus an AWD SUV are different. I drive just as fast on the highway but I approach sharp curves with more caution and I'm not taking it on canyon runs. Have you tried A/S tires on your SQ5?

If I had an SQ5 and lived in SoCal I’d be running Michelin Pilot Sport 4S summers. OP: you bought a high performance car, and you don’t typically drive where you need all season tires, yes? Why compromise your car’s performance if you don’t have to? We’re not only talking track use...a great tire will also be safer and give you the enjoyment you wanted when you bought the car.

I’ve owned a couple sets of Pirelli Scorpion Verde A/S plus. (Plus is new generation, better tire). Good tire, but not something I’d run on an SQ5. If you lived in cold weather I’d recommend summer/winter.

As for the summer tires, my research indicates that the Michelins are a step ahead of the competition. Just bought a set of 20’s for my Q5 TDI.

Appreciate your thoughts, Mythdoc. I'm still debating but I think I want to see what the Verde downgrade is vs the current Dunlop Sport Maxxs. If the only issue was cost, I would just do the PS4s, but I really like the idea of not wearing through tires every 12-15 months on my commuter and I think the Dunlops provide a loud and not particularly comfortable ride, so I'm curious if the A/S tires will provide a better experience there. Again, if it was a sports car like my SL500, I would stick with performance but for a commuter SUV that logs lots of highway miles that I bought for its versatility (as well as quickness and speed), I want to give it a shot. If I feel like I'm now driving a minivan and handling on my commute has suffered, I'll go with the PS4s in a year, they do seem like a better option than the Sport Maxx or P Zeros. I still may change my mind and go with PS4s now though, it's a tough call.