I purchased these recently in the cyan color - size L. I'm 6'1", 185lbs with 25.5" thighs. The shoulder straps felt a bit tight for my height but when riding they felt fine. The materials stretched beautifully to accomodate my thighs while riding so this size will fit anything from a thin to larger thigh. The thigh grips are about 1/4"(5mm), just enough to grip your thigh without pulling the hair. If you where larger than a 34 waist in pants, get the XL.
The chamoix is quite comfortable even though it has a low profile. My road bike has a thinly padded seat and I was comfortable on rides up to 3hrs. The cyan color looks great against a black or red top.
I highly recommend this bib for the performance to cost ratio. There's also the cool factor in blue....:)