sigma 17-50mm or 16-35mm for party work on 7D
I am hoping to buy a new lens for party work very shortly but stuck inbetween these two lenses. The sigma 17-50mm f2.8 which has optical stabilisation or the canon 16-35mm f2.8. I have always thought to get the 16-35mm but as I am young price is a big factor. Will the results and performance of the sigma (especially accurate focusing) be good enough for parties and general travel work.