And I've been there, exactly as you, but for the G version instead of for the R.
I must say that I like them all (5110, 5130 and 5230) for different reasons.
My advice is that you should try them on and choose the one that sings to you more, they wear and look very different on the wrist due to their different sizes and shapes. If I could, I would have the three π
As you mentioned, I also prefer the smooth and rounded case, so I discarded the 5230 (although the gray center is to die for). My very personal feeling is that the 5230 looks a bit more sophisticated and dressy, and I was looking for something more versatile.
I owned the 5110G before the 5130G, but when I had the opportunity, I couldn't resist the trade.
To me, the 5110 looks sometimes a hair small, which also contributes to a more vintage-ish look (which I loved, by the way).