Already being a Marine is definitely going to be a plus. Is it a guarantee that you will get an Air Contract, no. I can't speak for an OSO because I'm not one but here's what I've gathered about prior enlisted Marines who have applied for PLC and OCC. If two guys, one a prior enlisted(or currently reserve) and the other non-prior, were to submit their packages with the same scores (gpa, astb, pft) and the same recommendations then it kind of makes more sense for the board to select the prior enlisted guy. Again, I can't speak for the board but to me that just makes logical sense to me. Hope that helps somewhat.
Ryan,
Are you sure about those slot numbers? Those numbers sound kind of low to me. What district are you in?
Jaek