Replying to Tokina 11-16 vs. Tamron 17-50

Hey all, I'm currently in the market for a new lens, i have about 700 dollars to spend. I've been looking at the Tokina 11-16 which i know is a great lens but i'm really looking for peoples opinions on the Tamron 17-50, I think i could use the extra focal length but i would be mainly shooting with it locked on 17 on a glidecam. I'd love some feed back about both or even other lens suggestions, mainly for follow cams, maybe some tripod shots mixed in. +k for helpful information -Thanks!