I had the KW Sleeve Kit, and did 30 track days last season on them. The car performed very well, completely composed and consistent in performance. The benefit of a sleeve kit is you can corner balance the car and set-up the height to avoid the car raking forward. If you notice, static springs like EIBACHs or H&Rs rake the car forward to compensate for the front fender gap. Yes, the front springs have a different rate, but the momentum and weight of the car is shifted slightly forward. Lastly, for those living in four seasons, I raised my car during the winter months to deal with snow etc. There are definitive differences between spring only mod vs. a sleeve kit.
I recommend you get the Ground Control Sleeve Kit if you can, it comes with camber plates and a sway bar. I got KWs because I didn't want those extra things in the beginning (boy was I wrong
I can't comment on the comparison with ZCP since I modded my '08 with the sleeve kit. If you already have ZCP, you might want to see how that works out for you before tampering with what is a suspension designed for track use.