I like them both equally; I think Clapton has more of a fan base outside of guitarists, and has been a part of some very influencial bands (Cream, The Yardbirds, Derek and The Dominoes) but I suspect (and I could be completely wrong in this) that a significant number of guitarists would prefer SRV, because of the song's he produced, as well as his guitar and vocal tone.

I think Stevie had a lot more to come before he sadly passed away; Clapton's "Unplugged" was released two years after SRV's death and is personally my favorite album of his and (in my humble opinion) is some of his best playing...

I think this is a much fairer question than, say, Hendrix vs. Cobain, given that they played "simliar styles", (I'm not saying they're the same genre, but both are classed as blues-players) but it's still hard to judge when one is still alive and producing some excellent albums, whilst the other has to be judged on material written over 15+ years ago...

Just my take...