Just figured I'd post the info from Ben and Tim here - for it to not get lost somewhere inside this forum.
It's not really a review, but good info nonetheless:
"The Cold Sweat neck is fatter than the VHII and BD neck. The BD neck is a little sharper and offers a blend of classic power but with cut."
"The HD neck is slightly stronger than the BD neck, more sustain, smoother too. The RY neck is rounder, still quite strong, but classic too."
And here's the reply from Tim regarding the difference of the Mule / Abraxas / Emerald neck:
"the Abraxas neck has a little more output and more mid range compared to the slightly flatter response of The Mule.
The Emerald neck is darker in the mid range with quite a bit more output by comparison because it is wound with a finer wire gauge."