It's really hard to say, and changes with the day.
My '63 P is an old friend I've had for 40+ years, and it's a great, solid bass.
My gold top Epi Casady has a unique voice that I really like.
My short scale Gretsch Electromatic Jr Jet 2202 has a super-hot pickup and is a breeze to play.
My MIM Jazz in Midnight Blue is a very cool bass, and the E string sustains like the pedal on a pipe organ.
My Univox hollobody 335-copy is the prettiest bass I have, but it needs different pickups.
The P/J that I refinished and defretted is lovely, but I don't have a lot of reason to play it.
And I have a few others with varying degrees of attachment. I'm selling the Jay Turser 401, hopefully tonight, because I never play it.