Over time, having tried a lot of different basses the ones I've found that ergonomically fit me the best are G&L basses with skinny necks. Something about their neck dimensions and geometry just fits me perfectly. An SB-2/JB-2/L-2000/etc. four string with double-cut body and a #6 or #8 neck is a bass that I can play all day long. I have some tendonitis or RSI issues with my hands & wrists that make comfort a priority for me. So I have pretty much stopped looking at other basses and have been trying to isolate my ideal tone from a G&L.
All G&L basses sound good. Different, but good. In general they tend to the vintage end of the spectrum (as opposed to the modern end) and if they have MFD pickups (Leo Fender's Magnetic Field Design pickups) they will have massive low end, sparkly high end, great clarity across the spectrum and a ton of growl. If they have non-MFD pickups (Legacy/LB100, JB-2) then they sound like a good bass of that type with the saddle-lock bridge providing a ton of sustain as compared to many other types of basses. Tone is very individual and we all hear things differently and prefer different things. And add on top of that the effects of the rigs we play these basses through. So remember, the following comments are my take on what I hear as compared to what I'm looking for.
G&L rules:The L1K is that it fixes almost everything I don't like about an L-2000. It's pretty simple, passive and provides a limited, but very useful, tone palette. As always the closest thing to series (single coil w/bass boost on the L1K) is my favorite tone. I run into the same problem I always do with MFD humbucker equipped basses. The upper strings/range can get lost in the mix for me. I'm still working on whether careful attention to pickup/pole-piece adjustment and string selection can make it work well for me.
My L1K Bottom Line: Excellent basses. But MFD humbuckers and I don't get along - I'm happier with SB2s/JB2s in the long run.
The L2K is a great sounding bass with an almost unlimited array of tones available. My personal primary issues are that it is too complex and that it doesn't have a pickup blend. Those are, of course, essentially contradictory. One one hand I find the L2K too complex, I prefer a simpler plug'n'play approach. And the neck pickup in series is pretty much where it's at for me. But on the other hand I'd love to be able to favor the bridge or the neck pickups while still have the other present, but not all the way up (neck pickup full up, bridge rolled off until the sound "opens up" is my favorite tone on pretty much all other 2-pickup basses).
My L2K Bottom Line: Excellent basses. But MFD humbuckers and I don't get along - I'm happier with SB2s/JB2s in the long run.
With the SB-2 I really like it once I add a tone and a stacked master-vol/j-pickup-vol setup. This is my fallback bass that is simple, passive and always sounds good live. At times the bottom end can sound "hollow" to me (usually when practicing through headphones, live I always have enough low end) and it can be clanky/harsh (but that is what the added tone control is for).
My SB-2 Bottom Line: SB-2s just work for me. They must have a tone control added and at times I like what the bridge pickup adds to an SB-2 over an SB-1. I need to not sell any SB-2s and when I've spend too long with them only through headphone amps remember how well they work live.
The JB-2 gives a "jazz tone" and if that works for you then great. I like the OEM pickups in the Tributes but find the OEM pickups in the US JB-2s too "polite". But the beauty of the standard J pickup is there are a ton of variations out there to try. The balance is good, sonic variation is good enough and a good JB-2 sings throughout it's range. While punchy the transients aren't as extreme as from an SB-2. Adding a series/parallel switch gives another tonal option, albeit one that may have too much low end. So far a JB2 has never let me down live as long as I remember to turn the amp knobs up high enough to allow it to compete on even footing with other basses (the low output means turning the amp up higher to get the same volume which I have trouble adapting to).
My JB-2 Bottom Line: It's taken me longer but I've started to adapt to really liking what I can get out of a J-style bass. I like the OEM pickups in the Tributes but haven't liked those in US JB2s (go figure). With a series/parallel switch I find myself in parallel most of the time. I've always been able to get the clarity and cut-through I want out of a JB2 live.