After my years of playing and owning bolts- and neck-thrus, my general observation would be as mentioned above: I find that the neck-thrus carry more of the fundamental to the pickups, the bolt necks tend to be more of a low mid-range punch. Plenty bass to work with, but it just lacks that very last step (the fundamental and maybe the first harmonic). Of course the wrong amp would lose this anyway.
Sustain-wise, it's really a wash for me. Either one on a loud stage will carry as long as you want. Dead strings will choke sustain a LOT faster than the relative merits of neck attachment. And, too, it's a difficult apples/apples comparison as virtually all bolt-neck instruments are Fender-headed: The peghead is parallel to the fingerboard with no down angle, I'm sure string trees don't load the nut the same as a bent peghead.
In these days of basses having three-band EQ on board and amps having so much tone-shaping, I'm not sure how much of this matters in a ProTools/Bass Pod world. . . geez I feel like an analog dinosaur, I remember all the amps the Pod models!
I prefer neck-thrus for other reasons as well:
I like the strings' loading pulling the length of the instrument as the neck, instead of just neck having to fight the pull on it's own.
I don't like bolt necks as I do my own setups. It's a real pain to do bolt-necks if you have to pull the neck, remove the pickguard, etc., especially old-Fender style truss rods, where you've got that X-headed adjuster flush with the end of the neck and NO relief cut out of the body. At least MMan uses that wheel now. And it just seems prehistoric that the neck bolts are wood screws (no inserts/machine bolts) and I've got to use duct tape/light picks/whatever to shim the neck if I want more down-angle.
And I really hate zooming up the neck and sliding into that damn neck block. I love to turn my basses over and see the ski jump at the body joint!
J o e y
(Message edited by bigredbass on August 13, 2005)