I also had some weight-to-tone experience with my Spectors. My Kramer era NS-2s were solid maple wings and my Brooklyn era NS2JA was all the same materials but bolt-on. The result was more difference in sustain between these basses than between them and my Woodstock Helium Fortes. And that's because the core of the Spector tone is NT maple neck and the bridge but not the wings wood IMO. And as Jeff said, since there's no down-grade in sustain and tone using Helium bridge instead of the traditional brass bridge, the lighter options of neck-through NS basses sound basically similar to their all maple sieblings.
But it is not the case with Coda basses where the bridge is bolted to the body but not to the continuation of the neck as with NT basses. And here the difference in body wood will play greater role in sustain and tone, same as ash vs alder body of Fender basses.
P.S. a day before my friend bought my ex 1989 NS-2FL back from a guy whom I sold it to two years ago, the guy who was eager to play fretless Spector. It is incredible Kramer era fretless NS2 and it has a great fretless tone but it's well above 9.5 lbs...so after I took it and played it to test I thought it felt like a boat anchor after my Helium basses. So I thought to myself there's no way I'm going back to anything above 8.5 lbs since there're lighter versions available.