Mega don't forget to cash in your $50 rebate with dunlop for the new set of Q3s. You can go to dunlops website for more details and the form you have to mail in.
I have run both the S20s and the Q3s on both the street and track on my 13 ZX. As far as grip and tire wear, they are both about the same. I personally felt that the S20s offered a little more "feel" especially in the front tire and that minor difference is enough for me to be sticking with the S20s. Previously, I was religiously a Q2 and Q3 guy with my triumph.
Both tires really start to work excellent after they warm up. And I'm not talking about just riding, I'm talking about when your doing runs up and down a canyon or at the track. After your first run or lap, they really really start to hook up when you get some heat into the sides of the tires. Both tires respond sharply to tire pressure changes so if you are having handling issues or want a little more grip, start managing your tire pressures. A 2 pound change for me in the rear did a lot for me.
As far as tire wear, I started really being more on top of my tire pressures. I run track pressures even on the street because I'm so agresive but my tires were wearing out very quickly in the middle even though I don't commute . I started pumping up the tire pressures during the week for bike nights or 2 up rides and would reduce them for the weekend canyon carver rides. This gave me probably an extra 1000 miles on sets now. Although I'm getting even more now because I'm swapping out to slicks when I go to the track now so I'm no longer running them at the track.