Either PR2 or Conti 4000 GP (or 4000S). I've ridden lots of miles on both tires. My impressions are: PR2 - fast feeling in terms of straight line rolling, smooth but compliant ride feel and slightly on the firms side, and easier to mount when brand new; Conti 4000 - comfortable ride that doesn't feel as quick accelerating, better in corners, and harder to mount on rims initially but much easier for changing flats after they stretch.