You have probably found an answer to your question at this point, but to briefly respond to your post:
- Yes, ANCC does include theory, but IMO it's not something that isn't doable (I took my exam through ANCC)
- I did not take AANP, but have heard from those that did take it that it is definitely "more clinically focused" than ANCC (exactly what that means I cannot say since I did not test w/them)
- As far as being denied a job because you chose to test w/XYZ as opposed to QRS - that should not be a problem since most states/organizations/practices will accept both (it's very unheard of in most cases that you should run into issues w/that; that's not to say that it hasn't happened to someone...I just wouldn't worry too much about this)
Hope I was of a lil help to you. Good luck in whatever certifying body you choose!!!