Very different kind of a bass, the GW and the Crews-J5 - as I'm sure you know, the GW doesn't havea coated FB, and a much narrower string spacing. With my limited fretless-skills: the sounds were vastly different too - YMMV.
Regarding the Crews-J5, i've played a good few of them here in Japan. Sound is actually very close to a Pedulla, and the main reason I was looking at one was that that as much as I liked the Pedulla sound, the ergos in the Penta/Hexa buzz just didn't work for me at all. Sadly, Crews doesn't make a Jackson-six... but the five may be on the cards one day.
If you're curious about these basses - they're actually pretty abundant second-hand, and may not be that hard to get shipped to the US.
Another things to keep in mind is that the 'standard' J5 only has the rear humbucker pickup - the H+Singlecoil that Lobster has in his video is a much rarer variant (and that one IS very hard to find used). Having asked around in some of the music shops here, the consensus seemed to be that nobody much misses the front-singlecoil on the fretless, so they don't order/produce many of them.