I'm going to be buying an XTi as a first digital SLR, and I'm having a little trouble selecting a lens. I want something that's good for walking around and taking pictures of people. I'm not going to be doing portraits or anything - just people that I see about; general purpose, basically.
I've got it narrowed down to two lenses: the Canon 17-85mm and the Sigma 17-70mm. Each of these, it appears, has advantages and disadvantages - the Sigma has better optics and a fast aperture, while the Canon has a better, quieter autofocus, the extra 15mm of reach and image stabilization. I think I'm leaning towards the Canon due to its image stabilization despite its optical faults (distortion and chromatic aberration, which can be fixed in post-processing, right?) but I keep finding that shots out of the Sigma are a lot crisper and better-looking on the whole. For the same price - $1400 CAD - and bearing in mind that I'll also be buying the Canon 50mm f/1.8, which one would you recommend?
Also, are there any specific accessories that I should be getting, such as lens hoods or filters?
Thanks in advance for your recommendations.