Sigma 18-50 F/2.8 VS. Canon 17-85

[Outdoor23]

So many choices, but I have narrow it down to 2. Which one would you choose?? The Sigma 18-50 F/2.8 EX DC or the Canon 17-85 4-5.6 IS USM?

Mostly is going to be outdoor shooting. The extra 35mm from canon is good but not really a big factor. Care more about picture quality.

P.S. I know alot of you like the 17-40L, but that is too short and expensive for me, so maybe when I became richer....

[LightRules]

Depends on what you'll be using it for mostly and what kind of photography you like to do. I wouldn't use any TC on these lenses though.

[Headcase650]

I.S. in no way ever makes up for fast aperatures. I.S. advantage is limited to static objects, if your subject is moving, even slowly I.S. is usless unless it has a panning mode.

[buze]

Easy one. Sigma! And with the spare money, you can buy a 85mm f1.8 !

[CornMonkey]

i bought a sigma 18-50mm/2.8...and sold my 17-85. my sigma + my 85/1.8 >>>>> 17-85mm.

[accord]

When I bought my 20D, there was no inexpensive general purpose f/2.8 17-xx lens. 17-85 is my choice simply it is Canon. The image charateristics are the main reason I choose Canon system.

The yellowish of Sigma is not my liking. A lens profession (non-Sigma) told me that the Sigma 18-50 has a deeper DOF than odinary lens, therefore it look sharper than other lens at the same f number. The Sigma non-HSM lens uses direct drive of a large motor for focusing. It trade focusing speed for focusing accuracy. I do not have the expert knowledge to verify them. It would be nice if someone verifies them for me.

For the comparison of large aperture and non-shaky slower shutter speed (IS) for the same among of light intensity, I cannot say which one is better. They are for different purposes. Slow shutter speed can have motion blur, but shaddow DOF can also have out-of-focus blur because of object moving forward or backward.

So, which one will I choose if I do not have 17-85 IS?
17-35L+24-70L are too expensive, heavy and bulky: not good for general purpose.
Tamron 17-35+28-75 f/2.8 may be an answer.
17-85 IS is still on my list.
The Sigma 18-50? Maybe?! If I have the questions on this lens answered.