At age 28 you are not in a position to choose. I have heard from numerous sources that OASC will fail a 'youngster' in need of some maturity knowing that he/she is motivated and will return, especially if already serving in a ground trade. However a civilian over 25 regardless of how well educated has little chance of sucess at OASC second time around.
The jobs of AAC v RAF WSOp are continents apart and had you done sufficient research into your 'chosen career' you would know this already. When I first saw this thread (as your first post) my thoughts were, "Military troll seeks AAC v RAF bunfight" and I am as much amazed that this has not happened as I am amazed that AIDU has not given you direction to the sticky at the top of the page.
Notwithstanding what I have said, and if this is a genuine enquiry, you cannot go through life wondering what 'may have been'. Therefore my advice FWIW is for you to apply for OASC again, and at least if you get chopped you can put that aspect of your life into the archives. If doubt as to which service remains, remember that an application alone is not a commitment, and you can choose what to do with a positive outcome.