Results do not come into play with development, playing time matters. If a guy is "overmatched" at a level, it doesn't really matter - if he's getting good coaching, his ratings will improve.
I think it's important for your prospects to be promoted from time to time...they can become frustrated and may not progress as much as you want if they aren't promoted every season or 2. So putting a guy at AAA and leaving him there for 3-4 years isn't the best idea. That said, if you have terrible coaches at rookie and low A, I wouldn't hesitate to start my best prospect at High A and move him from there. To start someone at AA might be a little quick, but if you expect the guy to be in the big leagues in a few years, to start him at AA and then play 2 years at AAA wouldn't be terrible if your lower coaches are bad.