I'm in the process of trying out some of those things myself.
I've got both the unichip & the SBC-iD installed in my WRX,
and have got the AVC-R sitting around in the garage waiting for me to find time to install it. For the time being I've disconnected the SBC-iD solenoid and am letting the unichip control boost. Just deferring to the unichip is probably the easiest aftermarket boost control method of all (short of an MBC valve). I'm pretty happy with the Turboxs setup with no real complaints.
The SBC-iD does a great job but won't let you tailor boost versus RPM or TPS, so you can't deliberately taper boost @ RPM>5000. It succeeds at reaching your desired boost with minimal spiking, and is super easy to install & tune. The boost graph & replay modes are both very nice. Makes monitoring boost easy (an excellent but extremely expensive boost gauge).
The AVC-R is much more feature-rich than the SBC-iD, thereby way more complicated to set-up. Installing it is also relatively painful since you need to splice some ECU wires. I plan to splice into the unichip piggyback wiring to allow clean removal. This will keep things truly plug n' play. At some point I'll have to decide between the SBC-iD and AVC-r and get rid of one of them.
As for your question about what the controller does in the event of a MAP sensor failure... not sure how the controller would respond. Hopefully it's smart enough to prevent a broken loop death spiral letting boost skyrocket trying to hit the setpoint. In any case I prefer the Apexi sensor because it uses an electronic sending unit which you can position very close to the source, and it's an "absolute" reading meaning that it corrects MAP according to outside atmospheric pressure variation.