You're asking the wrong questions.
They should be...and not necessarily in this order:
1) What do *I* want to with the horse? What are my short term goals? My long term goals?
2) What am I capable of doing in terms of training? What am I not?
3) How much money do I have?
4) What are my specific criteria? (It seems color ranks pretty high on your list)
5) What are things I'm negotiable about?
None of these individuals are standouts, but all would be more than capable of doing a little of this and a little of that at the lower levels. The black and white mare has the best constructed riding hindquarter. The black and white gelding has the best constructed front end. The brown and white mare is equal in build front and back.