The Nailbomb is a super-clear, organic feeling pickup with a mid-heavy feel and lots of dynamics. It's 16k output, but you almost don't notice because it's so damn clear!
I haven't tried the Holy Diver, but I believe it is based on the Seymour Duncan JB, but with a far more balanced sound. From all accounts it's a great pickup, with warm but tight lows, and a really fat, sustaining tone.
That said, if you want that British metal sound, how about the Painkiller?
At the end of the day, always make sure you run any decision past Tim himself, either via email or phone. He is THE MAN, and always gives great recommendations.