Most arguments have been posted by now....
I wouldn't want to drive our Skoolie without one, especially when I'm alone. You can't see a playing child behind your bus in the mirrors!
A microphone integrated in the camera sometimes is very useful too! Most cameras, even the cheap ones, have this. Just like IR LEDs to provide visiblity in the dark.
A manual switch certainly has advantages over the reverse switch on the gear box.
A computer monitor isn't going to work (IMHO). To get a consistent picture with your mirrors, the monitor should have a switch position "mirrored".
Ernst & Sylvia