Warpig is the biggest, bassiest and most powerful pup in the range (asides from maybe the UberSinner and the Pig90 but those are special order. I did once have the idea of wiring two Pig90s into a humbucker but sheer amounts of routing caused me to think otherwise. Perhaps I could get try it in a warmoth build; Tim said it would be monstrous). Good for Jazz (all across the range), Death Metal, Regular Metal, Shred (I can recommend it; neck is great for a Satriani style tone when used with an orange Tiny Terror and an overdrive), Extreme metal, Heavy rock/blues. (list is non-exhaustive)
Painkiller is more refined for a sort of Judas Priest tone but can do Thrash, Trad metal, Hard rock, shred etc. In short it's more of a late 70's/80's pickup but someone will come in and correct me in a short while.
I can recommend the warpig neck for a lead player and a Ceramic Pig for a good rhythm sound (big mutes and chords).