For me, sure there needs to be a base level of physical attraction. When I browse the providers' showcases, I'm of course looking for what's physically attractive to me.
However, personality/mind very quickly move someone up or down the attractiveness scale to me. You may be super hot, but if you're a complete bitch (no offense to those who are into it), idiot, or just check out during your sessions, then that's a nonstarter for me. Conversely, if a provider may not be a hot young nubile thing, but is clearly intelligent and can carry a conversation as well as give a great experience, then that'll get me through the door.
Now when you get that amazing juxtaposition of the two... *dingdingding*!