It's a tough question. It's in situations like this that we need those tone charts! :?
I only have one of those four pickups, the Black Dog, but from what I've read I'd say
Brightest: VHII, definitely.
Darkest: BD, probably - it's dark but I wouldn't call it "sweet", it's quite aggressive.
Sweetest: Abraxas, I think - with the alnico IV magnet.
Not sure where the Emerald fits in - it's a bit hotter than the VHII or BD, more in the same ballpark as the Abraxas but I think it's brighter.