Anecdotal evidence has little forensic value. So P Basses are most common. As was the VW Beetle, but that didn't make it the best car in the world. P Basses have a sound of their own and it's relatively easy to have them well-heard in a mix without being too loud. For an old school metal sound I'd be worried a little though whether the P reaches down deep enough and whether its main strength - mids and low mids- won't collide with the frequencies of the guitars if brought out to their greatest effect. Iron Maiden's typical sound just proves that: Harris is much louder in the mix than any of the three guitars and he lacks ooomph/foundation (his busy playing style doesn't allow too much of that), but with three guitars beside you, you can stretch a bit. Then again, Geezer Butlers graveyard lows with nasty distortion on those early albums emanated forn a old P. But he had to fight for that sound with the then producer. Goes to show that a P Bass can deliver sounds not readily identified with it, but most engineers are too set in their ways to explore its possibilities.
My gripe with the P Bass has always been more about how it looks (plain, only half-designed, utalitaristic and unelegant) and how many there are of them than how it plays or sounds. In fact, if you can't get a sound you like out of a decent P bass, then you should perhaps pick up playing tennis. And if you consider the 34" scale one of the determining factors in the P Bass sound (which to my mind it is), then the world if full of P Basses from all brands, Gibson included.
Uwe