I'm going with Thomas myself with my likely-#1 waiver pick this week, although it's a bit of a moot point as Williams was scooped up last week.
That being said, I'd still favor Thomas over Williams despite his limited play time thus far. I like his QB better, and as another poster mentioned, the other receivers on his team may take some of the attention off of him.
(0.5 PPR, 12-team league)
QB: Vick, RG3
RB: McFadden, Matthews, K. Smith, R. Williams, M. Goodson
WR: Nicks, S. Smith, Britt, LaFell
TE: Hernandez, Pitta
DEF: Spot start (Cin in wk4)