I've been messing with iAP to Controller tunnelling and so far:
1. I can't speak to this, never used a RAP
2. Splitting is easy enough, the documentation doesn't quite match what I see, but it works fine.
3. Again can't speak to RAPs, but with and without Airwave the iAP operational state is pretty east to tell, just a different method from controller based connections.
4. I believe there are iAP with 3G and 4G backup methods - given all the setup pages for it in the GUI (I haven't got those models)
5. Revocation of the iAP is easy at the Virtual Controller (cluster membership) and at the Controller (VPN/Tunnel connection).
It's probably much more a matter of familiartiy than of technology at this stage. Do what's comfortable if it delivers everything you need, start heading up the learning curve if you need more/different functionality.