most of my basses are pj's, but i find myself using only the p pickup more and more. i do like being able to dial in some j tones when needed, but honestly i could be perfectly happy with a precision and no j pickup.
+1
My roundwound/fretted bass is a PJ. Most of the time the J pup is rolled off.
As for slap, there have been a ton of P-bass slap tunes - predating Marcus of course. Another take on the gold-standard:

