Save a bit of coin and get the G4. The G5 isn't seamless in monitoring two different bands as a lot of folks think. It IS good for conventional paging, then steering to a trunked system for further monitoring. EVERYONE I personally know with a G5 here in the Houston area just ends up using the 7/800 band exclusively and dedicating another scanner/radio for the VHF or UHF conventional stuff.
This is assuming of course you are "scanning" or monitoring as a hobbyist. The G5 can be a great tool for FD personnel.