I use both. Fat boy has a thicker handle the SS has a thinner handle. One is adjustable the other has a fixed head. It is a matter of preference I like the shave I get from both, the fatboy might be a tad heavier. I believe the head design is the same with the exception of the adjustability option of the Fat boy. I did not know how the shave would differ until I shaved with both. Some will say they like the SS over the Fatboy and vice versa. I like them both and get I get great shaves from both. Someone may correct me but to get the same blade exposure on the FatBoy to be the same on the fix head of the SS you have to dial up to somewhere between 4-6 but I am not sure since I have my adjustables set to 3 all the time. I am sure someone with more experience will chime in. I say get both and enjoy them. I do.
[I]"A well lathered face is half a good shave"[/I]