I think either something like Warpigs or more PAF-like would both work well for stonerish metal -- you'd just get a different emphasis in the tone. Basically, I think you just want to pick something other than the more cutting, higher output metal-orient pups. You want to stick with something that has plenty of mids and low end.
There was a good point made a while back by ... argh, I'm blanking on the username ... need more coffee ... nevermind! Anyway, the point was that you can get a fairly awesome stoner tone with closer-to-trad output pups (Mule, Black Dog, Emerald, etc.) and cranked valves, particularly pre-amp valves. OK, that's hard to do at home unless you live in a bunker or have one of those clever low-wattage amps than you can saturate without killing all lifeforms within 300 metres, but you get the idea. Classic Iommi stuff, for example, doesn't have huge output pups or super-high gain. And he used P-90s on the early Sabbath recordings didn't he? So don't discount those Mississippi Queens (or go all the way for the Pig-90! :twisted:)!
That said, I think Crawlers would work well too -- better than the Abraxas, I think, and almost certainly better than the RYs. I've got a Crawler set, and tones from Kyuss and Cathedral and such were among my touchstone references when consulting with Tim about a pup choice. I wanted something that would take me to those places, but without sacrificing versatility to go other places a well -- and the Crawlers suit that bill, being basically a hot PAF with extra midrange grunt. (Similar to the Abraxas, though they're more straight like a hot Mule/PAF as I understand it.)
I've got a stoner-vibe song I quite like -- total Kyuss-meets-Monster-Magnet-at-a-Hawkwind-convention rip-off :) -- though my only recorded version predates my Crawlers. I oughta re-record the guitars and post it. (I wouldn't hold your breath, though -- I'm a slow recorder! ;)).
That's my tuppence, anyway!