I would argue that if someone looks the part, then they can be successful with a lower level of skill, and so they have less incentive to really be as good. My impression is that people generally, and doctors in particular, are quite lazy and generally aim to only be as good at a thing as they need to to get what they want, so the guy who looks the part is likely to be less competent.

There will be exceptions obviously, but I know that if I meet someone who puts a lot of effort into appearances, my presumption is not that he does this because he is incredibly hard working and just puts more energy into everything. In my experience that's not usually the explanation.