I wonder how the battery life for a handheld scanner compares to a transceiver being used as a spotters radio. You tend to sit there quite a while with the handheld scanner so it is built for low battery drain. At any rate, if you get the transceiver get a couple extra NiCad battery modules and carry them in a sandwich bag.

Early Cubs and other pre-radio airplanes need a handheld, but otherwise I agree with Otto- just skip the backup transceiver because the likelihood of needing it plus having it ready to use, is seriously low. The only exception I can think of might be offshore flight in an ASEL, which is nuts if you ask me. In that case you might want a marine VHR radio to help ships find you and most handheld transceivers don't have marine band anyway. I think Japan Radio Corp (JRC) has one with it, but not Vertex or ICOM.