i own a GSG-5 and ar-15(not .22 though)
i think in terms of fun factor i think GSG-5 wins
its light it looks cool and just fun and i think those ar-15 .22 look kinda weird maybe because i own a real one...
accuracy i think is around the same (but what is "accurate" for a .22 for you? if you're looking for real accuracy go with something else like a 10/22 but expect like groupings no less than 2 inches at 25 yards with GSG-5 which is not bad but not good either haha)
as for reliability i've shot a few hundred rounds through my gsg-5 no cleaning and no problems thus far
cant go wrong with either
in the end its what your little heart desires