Jeff
The turn performance of the hard wing F-4s (USAF C, D, and E) was pretty much the same. When turning the E, the nose felt like it had a longer moment arm (and it did), but turn rate wasn't affected.
The effect of slats was not so much that the jet turned better...the primary effect was that of removing adverse yaw as such a significant factor if aileron was used at high AOA. The slats made the jet much more forgiving when using aileron while pulling G.
The slats also produced a fair amount of drag, so energy bleed rates were higher. How much? I don't really remember. There was a group of "hard core" guys that preferred the non-slatted jet because it was faster and lost less energy. Others (me included) thought the slatted jet to be a better "dogfighter". But I do not have any hard data to say one way or the other.