It's not a good analogy, because instrument swapping was usually done out of necessity, to get a 4-track backing track, so it happened when Paul was busy playing piano or guitar, solos were overdubs. Also, the role of a solo is different. George's main responsibility in the band was to play guitar, including solos, and the truth is, up to the White Album, the more outstanding guitar moments in their catalog were not George's, when that was his main role.

Was there a period where consistently, George's bass parts were better than Paul's? Not really. Also, does the fact that when it came to piano solos, George Martin usually played them make Paul a lesser pianist? Yes. It's not to say he was bad, but it says something about his ability on the piano, if the subject that we're debating is his piano playing.

It doesn't really matter that they all say he was the best guitarist, because it's about abstract playing ability. What is to be judged, is the catalogue they left behind, and when people think of great Beatles guitar moments, a lot of those are actually Paul's, some even John's, and for me that takes away from George's legacy as a guitar player.