Actually, I've tried on both Radars and Radarlocks and have found that the Radars provide a slightly tighter fit. Not sure if your Radarlocks were tighter, Nate, but my Radars were...
They're both great shades, though. The cool thing about the Radarlocks is that Oakley released a number of new frame colors previously unavailable with the Radar. I do, however, prefer the fact that the nosepiece (outer part on the lens, not the unobtainium portion) of the Radar matches the frame vs the standard, generic, "black" colorway of the Radarlock nosepiece.