well, i have a warthog, and it's very very good- but i haven't tried any bk's (yet! :twisted: ) :(
i think the general consensus, around any of the other forums i'm on is, swinesheads are EXCELLENT value for money, and very, very good (they beat the cr@p out of any dm's or sd's i've tried by quite a bit!)- but if you have the cash for bareknuckles, they're the ultimate.
and fwiw, the warthog isn't really a metal pickup. You'd want the xbucker for that- but it's maybe not the "tight" sound you're after- it's meant to be very bassy and chuggy, for want of better words... EDIT: it's certainly not muddy though, from what i hear
if you have a gibson les paul, i'd say it's worth bk's, IMO... if you had a £200 or £300 guitar, i'd say swinesheads (that's my philosophy, anyway)- i'mn definitely going to get some bk's, but i'm waiting till i get a kickass guitar to do them justice!
EDIT: I don't mean that bk's won't work in or improve a £200/£300 guitar- of course they will! But IMO if I'm willing (and I am! ;) ) to spend around £150-£250 (depending on pickup config.) on a set of pickups, I'm also willing to spend £600+ on a great guitar to make the BK's even better!
now i just need the "headbang" icon...
hope that helps!