I am not sure on this one, but I think that
the Boss GT3 is better than
the GT5. I know the GT3 is the newer one and has more options, like pickup emulators, speaker modeling etc..
The POD is better for recording, no question. I have used the GT3 vs the POD straight up. Better sounds, easier...etc.
For live, toss up, either pay for
the floorboard with the pod, or just use the GT3 but the emulations are not as good..
Rackmount pod, yes, POD PRO. Costs 600$ US.
Lot of money for added XLR and rackshape.
MIKE