I worked it out long ago but by chance.
Stumbled into P bass ownership in about 1988. Maple board, alder body 1978. Loved it
Bought another, this time rosewood board. again late 70's. Loved it even more.
Then started playing a JayDee Mark King. Hated it. Too much to fiddle with and I lost my way.
Then a hamer Scarab. Wonderful bass, didn't like the sound
Squier JV jazz bass. Yeah not bad at all
Then I found my '73 P bass in london. Traded in an Aria SBR-150 that I didnt like the sound of. This rosewood board, alder bodied bass became my goto for nearly 25 years. Others have come and gone but this is it.
Ampwise, Trace Elliot, yeah ok I suppose, Then Marshall Jubilee 300. Very good. Then another Trace and it was average again.
Then Hartke HA3500. Loved it with its transporter 4x10.
Then I bought a Musicman SUB stingray. Absolutely hated the sound until one day (so confused about settings) I set the amp flat. BINGO, a real lights on moment. Just a slight tweak here and there and it was amazing. What ever I plugged in sounded good. My 73 P bass was even more awesome.
If in doubt I go back to my 73.
These days ampeg PF-500 into a small Mark bass 1x15. Ultra bass switched in and the rest fairly flat. It's as good a sound that I've ever had. My Flea bass sounds ace through it as do all my police basses.
But again, alder body, maple neck, rosewood board and the pick up in the Fender sweet spot and I'm happy and I know it will work for me