The geometry is different. The SS has a very pronounced lip that is supposed to help stretch the skin a bit, but in practice kind of forces you to use a slightly steeper angle of approach. The SR is the newest model and tones down the lip quite a bit so it feels a bit more natural to use. The SR also has more weight to it. I generally prefer the SR after getting it but revisited the SS again lately which was fun to use as well.
What’s different between the SS and the SR (except the fancier handle)?
The geometry is different. The SS has a very pronounced lip that is supposed to help stretch the skin a bit, but in practice kind of forces you to use a slightly steeper angle of approach. The SR is the newest model and tones down the lip quite a bit so it feels a bit more natural to use. The SR also has more weight to it. I generally prefer the SR after getting it but revisited the SS again lately which was fun to use as well.
Here is a great page comparing the various offerings.
Thanks!