I say we just keep the default FemShep that we are used too, but since that isn't a part of the actual question I'd have to say that;
I quite like 5 and 3, reason being that they are the most aesthetically pleasing (in my opinion). 5 looks like your average hot spy/commander girl and reminds me somewhat of Gears 3's Anya. 3 reminds me of ME 1 Ash, which yet again is a generic soldier girl look. Both these characters look generic, average, but most of all safe, meaning that they don't take any risks in the appearance and therefor avoiding mass hysteria when the game comes out and people hate the look. The player is the one to choose her identity, and (Bioware) making her look more personalized than generic (in my eyes) removes some element of choice because you sort of expect her to be a character, not your personal character that you develop, but a character that you just happen to play, if you know what I mean.
Mind you that I am writing this at 04:20 a.m and without much sleep my judgment can be a little, shall we say, clouded
Now that I think of it, 5 with slightly shorter and black hair, but same haircut would be kinda cool too. A little mix between ME3 Ashley and the default FemShep from ME1/2.
Bye bye sleepy now