Quoted from jemsite "The neck profile is a bit thinner (front to back) than the traditional JEM neck as requested by Steve Vai. It is described as unique to the JEM but "kind of a Wizard neck at the nut but not at the 12th fret"."
I happen to own both the dbk and a prestige 2550 and 1550 and the neck of the dbk feels "bigger" for certain. Maybe it's slightly thinner but i don't think so and it's definetly a lot wider. Perhaps it differs between the years of manufacture as well?
I've never played a vdy though.
Anyways it's a really nice guitar.