I myself am in the market to buy a GW fretless, and have actually ordered the GWB205. There is a video of Gary playing the GWB205 and that is exactly the fretless tone I have been after. YouTube and and good set of headphones are of some help to hear the differences between the basses, although that is somewhat subjective to the quality of the recording. I am surprised that, while I can find several excellent reviews on the GWB1005 and the GWB35, I cannot find where anyone has reviewed the GWB205. There seems to be more of a market for this bass in Europe, but even there nobody has posted any reviews online. If I could afford the $5k I would gladly go for the GWB1005. The GWB205 is a closer cousin in the sound and features. The GWB35 does sound quite similar, but maybe not quite as warm. But that bass does not have a Bartolini pickup like the 205 and 1005. That pickup is not radiused to match the finger ramp like the 205 and 1005. The finger ramp on the 35 is plastic and more difficult to change the height of it as opposed to the wood finger ramps. The GWB35 also does not give you the option to switch out of the active mode to a passive mode, whereas the 205 and 1005 gives you the choice, which obviously gives you more tonal options than the 35. The GWB205 does cost $900 more than the GWB35. Is the tone that much better? That will depend on your ear, your equipment, the venues you play and the styles of music you play. From what I have heard on YouTube, the tone is close enough to where I am still debating whether or not the extra coin. There is an obvious similarity in the tone of all three instruments, and we have Gary to thank for that. At least he has made the "Jaco" sound (which these basses just nail!) within reach for most everone. I am still leaning towards the GWB205 which is so very close to the top dog GWB1005. It does come with a $100 Ibanez hardshell case which the GWB35 does not offer, so comparing bass to bass the 205 will cost me $800 more for almost identical features as the 1005. So I am trying not to think of it in terms of spending $800 more for what would not be described as a huge improvement in sound, but rather the fact that I am getting almost the same exact sound of the GWB1005, which I have seen online for around $4k, for a savings of about $2500. So that makes the 205 more worth it to me.
I know this is not exactly the answer to the question you posed. I have played a beautiful Carvin fretless neck-thru for about 25 years and it has a great fretless tone that I have gotten many compliments on, and the two pickups DO offer quite a range of tonal options that I probably won't get with the GWB's. However, I have been trying to get that fabulous tone that Jaco has made us all drool over and have not been able to achieve that with my current 2-pickup bass. But every recording I have heard online of the GWB's, even the 35's pretty much nail that elusive sound at a cost that in many cases is far less than what you would spend on other manufacturer's offerings...and I'm not sure I would get that sound with other manufacturer's basses. Yeah, they would sound like a fretless, and sound great. And maybe that is what you are after. But if it is Jaco's sound that you are primarily after, the GWB's...all three of them...will nail it for you, with incremental improvements in tone the more you spend, as is pretty much the way things go in life. Hope that helps you, at least somewhat.
While I am on this post, I would LOVE it if anyone can send me any kind of a link to a review of the GWB205. Can't figure out why such an excellent, "Premium" bass like this would be totally ignored just because there is a bass that Gary made perfect (for a lot more money) and a model that is much better than your typical entry-level fretless that most people will buy. I have a GWB35 budget but an ear and appreciation for the best, making the GWB205 such an attractive option. Thank you.
