Well it really depends on what sort of sound you're looking for. As far as I can tell they are both awesome for metal, just in slightly different respects.
The nailbomb has quite an organic sound, better cleans than the warpig. However, the warpig really is the shizzle for extreme metal. Really bassy and fat. I would email Tim and ask for his advice, he knows what he's talking about. For chimera maybe the warpig would sound best.
Personally I went for a nailbomb for playing stuff like opeth, slayer, etc. but still waiting for it to be delivered
