Yeah, the HRR has the QuadraCut System while the HRX have the MicroCut Twin Blades, which cuts even finer. Obviously, though, I'm not going to run out and buy an HRX having just bought my HRR.
Can you put the MicroCut Twin Blades on the HRR? I'm guessing not. Hence my question about the Gator blades, which some people rave about, and are only 15 bucks.
Incidentally, my HRR does have the Roto-Stop blade brake, that's not exclusive to the HRX series.