Sorry, I did actually mean G&L SB-2 as I was thinking about the G&L JB-2 in my head
Hamfist also gave me a very detailed and valuable feedback from his real life experience so I'd take the initiative to share with other newb who might be wondering the same questions...
"I assume you mean the G&L SB-2, which I would class as the least competent of these 3 basses. It's OK, but simply nothing special IMO. Tonally, it just felt weak to me. Who knows, I may have got a bad one as others speak highly of theirs (although these are mostly the USA ones, not the tributes). I felt that the basswood body and an overly flimsy neck affected the tone negatively.
The TRBX504 excels if you really like a twin humbucker bass with a slim, Jazz-type neck, and light weight. For me the active preamp (the pickups are not active, just the preamp, like the 44-01) in the Yamaha is nothing particularly special, although it's OK.
As a bass, I preferred the Lakland, though, although it is fairly heavy (whereas the Yamaha is really light). The Lakland has a slightly wider, chunkier neck, which you may prefer or not.It is still nothing like a Precision neck though.
I thought the neck pickups on the TRBX504 and the 44-01 were both glorious for dirty rock tones. The Yamaha becomes less competent the more of the bridge pickup you dial in. I just didn't get on with it's bridge pickup really at all.
The 44-01, I still really liked a lot of it's other tones than just the neck pickup one.
If someone offered me one of those basses I'd go for the 44-01, but the TRBX is a very competent bass and so much comes down to personal preference and taste."
Again, thanks everybody for your feedback... and I am now waiting for an opportunity to jump on an 44-01...
-Wild