Casting a dancer…

When choosing dancers for a new piece, what do you use? I mean, the easier answer is you cast according to each dancer’s technique. But let’s think about two dancers with the same movement style. And two characters completely opposite to each other.
And this is a real problem for me right now, so feedback, more than welcome, is needed!
In this case (and probably in general), we have two options to cast the dancers, according to their personality or according to their appearance.
Amazingly in this case, the decisions to which I arrived after considering these two option are also opposite… One dancer has the personality for one character and the look for the other, and same with the second dancer.
What is more important, then? For the dancer to look exactly as the character? Or for her/him to feel more identified with what (s)he has to do?
I believe that personality really comes accross, specially if you don’t really want dancers to “act”. But obviously appearance is the first thing that audience perceives…