I have used SP2s and M7RRs on trackdays and both have done a good job. My laptimes on them are usually in the lower half of fast group riders, I know the tyres could do better, its my bottle that gives in first. The SP2s were marginally better in the dry, rubbish in the wet, and wore out quicker than the M7RR - which are still v good in the dry, good in the wet and seem to last for ages. Never had any issues with getting the tyres working well after a couple of minutes on circuit.
One thing to consider (and I am not a pro racer) is that slicks will lose temperature when you are on track if you are not working them all the time, its all well and good having warm slicks for a session but if you are not lapping fast enough its gonna get interesting....