OK, the Warpig is a compressed high output pickup with a lot of bass and low mid focus and great clarity in those areas. It does not have a lot of highs / high mids, or at least is biased towards the low end so the lows really come through. As a result its great for down tuning and heavy stuff, and shines under high gain.
I play a bit of everything really - old school rock and punk, blues and early to more modern metal (80's / 90's / 00's thrash). Metal is covered nicely end to end by the Warpig, if you like that chanky heavy sound, but it is out there with the low end. If your chap likes his bass, then maybe the Warpig is the way for him to go. The '80s / '90s thrash stuff I play though is however better handled by the Painkiller I have - it is more high mid focussed and can really nail those '80s / '90s metal tones.
I can get a passable old school metal / punk tone from the Warpig, but IMHO its not the Warpigs thing really and there are better BKPs for that sort of sound. The Warpig is compressed and tight, so misses some of the sparkle and dynamics you see in lower output pickups when I use it with less gain.
So I guess if your fella wants a high gain, heavy, tight, low focussed and compressed sound then the AV Warpig will be great!
If however he values a (slightly) more balanced, open and dynamic sounds for the old school / punk area then a Nailbomb, which is also heavy, just not as heavy as the Warpig.
BTW, I judge "heavy" by the ammount of compression / bass / low mids in the sound.