Digging a bit further, now that I'm more or less fully awake, seems the difference in the seals is that the SR are missing an inner seal that the R have. Of course, the chance of getting contamination from inside the frame is less likely if there's no ingress opening for dirt and whatnot. Also, seems the SR cups are hard anodized while the R are not. That's what I gathered so far without speaking to someone from Campy.