Do you expect to hear a non-biased opinion in a site dedicated to Musicman products? Most people around here are MM enthusiasts. It's like going in a Rolls-Royce club and ask the members "which car is the best in the world?".
Maybe the better question is, "What's the best value?"
You can spend 4 or 5 thousand dollars with some of the boutique luthiers, and I've spent some - for me - shameful amounts on USA Laklands and a Fender Custom Shop Jazz, but is the difference between, say, a regular MIA Jazz and a Custom Shop Jazz really worth it?
Man, 2 years ago while the good ol' bass centre in London was in Wapping, I was about to enter when I heard from inside some REALLY funky slapping. There was this cool bald salesman showing some licks. The sound was so cool I was convinced it was a StingRay. When I only got closer I found out that it was an OLP!
lots of it is personal preference. I know guys who's preference is an active 24 fret, so they use spectors, warwicks, etc. As bovine said, its up to you. I am very surprised in the amount of people saying the olp is the best sounding bass to them . The best sounding bass I have ever played, would probably have to be a dingwall prima 5. Although I do still love my musicmans obviously. Keep in mind that I have not played many boutique basses like fodera or alembic or sadowsky, so can't really comment on those. Also can't afford them, but for basses that the average joe like me can afford, I loved the stingray that I found, thats why I got it!
My Ken Smith BT5G - Low-low-low action and great "darker, smooth" sound that blooms when you hold a note. Lots of exclusive features on this Boo-teek
My MM Bongo 5 - Great all around IMO because the hi-mid and lo-mid makes for a plethora of variations - fantastic high-end snap
My StingRay 5 Lined Fretless - Nice mwah and very easy to play due to the "cheater lines" as my wifey calls them. Fits in very well with our slower, worshippy stuff.