Drew -- Thanks so much for your input. I should have made my point clearer, that is, I meant not a "prima ballerina" (like Fonteyn, Makarova, Maximova, etc) but generally, a principal dancer. I was interested in the differences in the qualities, technique, personalities, (whatever the elements are) that distinguishes a principal dancer from a soloist or a first soloist. For example, I think Karin Averty really deserved to be principal dancer (but besides all the problems with her & POB administration) she was never promoted. But whatever the reasons are, perhaps there really was something lacking in her dance movements/style (I really don't know how to describe this ...), because I think truly exceptional people do get promoted. Anyhow, I hope this is making the question clearer...!