I have both sets in identical guitars (which I use for gigging). There may be guitar differences, but what I hear under 'classic rock' gain levels is:
The VHIIs are thinner sounding. They're like a beefed up single coil and do a great "Tele on Steroids" sort of sound. Powerful and distorted, but clear and clean at the same time. Very Van Halen-esque.
The Holydivers have more mids and thickness, and really sing. Classic powerful humbucker sound, and very punchy.
Played clean, the VHIIs have more 'spank' and are quite Fender-like. The Holydivers are similar but much warmer with more mids.