I like 'em both.
For sitting around playing at low volume with a clean or just-breaking-up sound, single-coils are best, no doubt about it. They have that open, airy quality.... I don't think a clean humbucker sound is ever totally satisfactory, the high notes are a little hard and characterless, the bass a little too boomy.
On the other hand, with a dirty sound I prefer humbuckers. When single-coils get mushy, humbuckers start to sing. They have that power and crunch. And nothing sounds as good as a neck HB with the tone rolled off.
Then again, maybe my favourite sounds are in the middle ground. I like lower-output HBs with a bit of definition, not too bassy. I like vintage-hot singles, not too piercing. I like P-90s, I like minibuckers. And - shoot me down in flames if you need to - I even like stacks and single-coil sized humbuckers. They have valid sounds in their own right. Not everything has to sound like a '57 Strat or '59 LP, so long as it sounds good.