Disadantage? Full length guide rod, you need a paperclip (AKA take-down tool) to disassemble. While paperclips are common-enough, you just may not have one with you the one time you need to field strip the pistol.
Advantage? Still trying to think of a real one.
I know that some claim that the added weight of bull barrels can do wondrous things like help with recoil so aim & follow-up shots are easier, but I doubt that it contributes much if anything. Bull barrels may help with lock-up to the frame (accuracy), but a well-fit bushing can do the same thing.
Thickness of barrel has nothing to do with accuracy, any barrel can be rifled to very high tolerances if the manufacturer wants to.