0-28 so far. Not looking good for this question. 

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.

If you read all of the help and dev chats, I think you'll find contradictions.

It says -
- players should be at the appropriate level
- better coaches result in more development
- players should be promoted to maximize developments

It never says if you're better putting a draft pick at AAA for 3-4 seasons (assuming AAA coaches are the best in you MinL), or if you should start them in Rookie and move them up every season.

I suggest you look at some successful teams and GMs and see what they do with their prospects.

Project when he'll be a BL player and plot his minor league career that way.   I've found it does no harm to keep a guy at a level 2 seasons.   Players should be in AAA when they're added to the 40.

RL/LoA/HiA - Rookie and first full
AA - 2nd/3rd full
AAA - 3rd/4th full.

If you think he only needs two seasons in the minors, and I know some people say "OMG!!!  ONLY TWO SEASONS IN THE MINORS?!!?!?",  AA/AAA for those two seasons.