I too like both, but I think I'd go with Sableye. Its design is sort of sleek and understated (apart from a bit of bling, but hey, we've all been through that phase), and I like that he's found himself an interesting niche in the metagame. And yeah, look, Spiritomb... just one of those Pokemon that I've had zero engagement with. I like his concept because it's a bit dark, but then I feel that he kind of fell over in terms of design - he looks like a bit of a psychedelic mess, whereas he could have been maybe a bit more sinister, with such a bad-ass premise behind him.