Sub brokers are required to get registered with NSE too (in most of the cases) and moreover they are required to deposit a certain some (negotiable and varies with each company and sub-broker), sub-broker get a trading terminal on which they can trade for their clients just like a branch does, and their share of profit is negotiable and does vary in each case
Whereas AP are just required to fill an agreement form with broking company, often they are not required to get any registration done with NSE nor they are required to deposit any sum with the broking company and their share is often fixed (mostly at 20%) and most important they are not authorized to trade on behalf of their client i.e. they doesn't have any trading terminal
hope it helps