From another thread about BKP-neckpickups:
Here are some really interesting quotes after further inquiry with Ben & Tim on neck pickups, that I would not want to keep to myself, as I'm sure it can be of good help to anyone researching these models:
"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."