I personally prefer JP's compositions/writing, as his material often has more meat on the bones, it's more memorable anyways (to me). However I prefer GG for pure lead/melody/solo playing (and it goes without saying JP is no slouch here too, lol), as his note selection and execution are equally inspiring (but then again, I actually prefer Greg Howe over GG when it comes to that type of music so what do I know).
We need both on the plate. They're different animals.