JP, I can finally help you with one part of the equation, as I played a Nailbomb the other day.
NAILBOMB vs. DUNCAN JB -- Bass Response
The only SD pup I've owned that has an output similar to the Nailbomb is the BJ ... I mean, the JB! PDT_008
In terms of OVERALL OUTPUT LEVEL, the NB has way more low end chunk and grind. For extreme metal, I think that the Nailbomb is probably the ideal pickup. (Have never tried a Warpig, so I can't comment on it)
The NB is what I would call a 'distortion' pickup, in that it will drive your amp's preamp stage to overdrive even if it's set to be clean. There is a lot of talk about the versatiity of the NB, but I can't comment on it since I'm not a versatile player; I play metal, that's all.
Since the NB has an alnico magnet, it does retain some dynamics and headroom. The harder you play, the more output you're gonna get. However, on Wednesday, the amp was breaking up even on the clean channel. That says more about my lack of ability to play softly than about the NB, tho. I'm not a whacker, but I do have a certain amount of attack in my playing.
Is the bass tight on the NB? Sure, why not. There IS a lot of low end on the pickup, tho. Do I think that the bass is tighter than the Miracle Man? No. Do I still think that it's a better pickup for death metal? Yes.