I have 6 basses - an 80s pre-Ernie StingRay, a 2013 Sterling SUB 4 (defretted), a 2012 Ergo EUB, and saving the best for last, a 90s MIM Precision that used all American made parts and was just assembled in Mexico (rare), a 90s all Koa Carvin fretless 4 (the sweetest sounding bass I have ever heard), and my main bass, a 90s Carvin LB75 fretless.
The Precision sounds so much like the original 'Ray that it is eerie. After the original preamp failed, I replaced the Carvin Koa 4 with an Audere. Wonderful choice. Not loving the preamp in the LB75, I changed the mag pickup preamp to a DarkGlass Tone Capsule (OMG!!!) along with a GraphTech preamp to mix the piezos with the mag pickups. The sustain is ridiculous, and the tone, for the first time in over 40 years of playing I can truly say I can get any tone that is in my head to come out the speaker.
I have to say that the sound is certainly the result of a combination of the quality of the bass(es) along with the high fidelity output of the Trickfish Bullhead 1K running into a Schroeder 1210PL. I run the amp absolutely flat, and do all the tone adjustments on the 5 string itself.
Like other people who have posted on this thread, I can hardly judge based on such a tiny sample size, but I can say this - if I could find a 90s Carvin fretless 6 string that was configured similarly to my LB75, I would snap it up in a hot second.