Looks, for me, have nothing to do with a Master (for like what most of the others have said, it is mainly in the eyes). However, that being said, an initial feeler session for the right person would probably start with the more physically attractive ones and then drift to the intelligent ones. Don't get me wrong...I will always wind up with the ones 1) older than me by at least 10 years (I am 28) 2) intelligent 3) at least 6 feet tall and 4) stronger than me. But as for initial interest, I would probably do the shallow thing and be more likely to at least approach and keep a conversation going with someone that I thought was physically attractive.
For the record, my Master was not at all attractive to me when we started our relationship, and he gets more and more so as the relationship grows :-)