I have sat on a bunch of sport bikes and for me the cbr's are the most comfortable. the daytona was the least. the rest fell somewhere in the middle.

the naked bikes don't look quite as cool as the sport bikes but they are even more comfortable still (because you sit more upright).

I have not sat on the rc51 but I have heard they are a bit taller and less comfortable (I am 5'7").

I am trying to decide if I want comfort or looks. I am not going to drive any of these bikes to their limits so that is basically what it comes down to.