I think the sharpness of the actual cutting edge depends on the steel used, the inclusive bevel angles, and how well they meet (i.e. level of polish/grind). The edge, sharpness wise, doesn't care how much mass is behind the bevels.

Flex-wise, the amount of steel behind the edge (full-hollow vs. wedge vs. "singing" grind) has a major effect on flex, but little effect on edge sharpness. The thinner grinds do sharpen up faster (sometimes) because there is less steel to remove.

Basically, I agree with hi_bud_gl. I just like to make it sound more complicated.