Which lens, Sigma 17-50mm f/2.8 vs Nikon 16-85mm f/3.5-5.6G?

Which of these lenses do you think is better? From examples I have seen the Nikon seems to take much richer, more accurate pictures with better color detail. While it does have a wider zoom range as well that is not one of my considerations.

But the sigma is still very good picture quality with a wider max aperture for blown-out backgrounds. It should be noted that the sigma also seems to over-emphasize yellow colors though.

They both cost the same price ATM. I won't be getting it soon, just thinking ahead for when I feel I need a better lens.

Added (1). Mind specifying how the constant 2.8 is a bad thing? That is just the minimum, it can be set higher.f/3.5-5.6 mean that at various focal lengths the minimum is different.Am I missing something?

Added (2). The glass affects color. I'm sure the body has an affect on color, but so does the lens.

"The front element is critical to the performance of the whole assembly. In all modern lenses the surface is coated to reduce abrasion, flare, and surface reflectance, and to adjust color balance. To minimize aberration, the curvature is usually set so that the angle of incidence and the angle of refraction are equal. In a prime lens this is easy, but in a zoom there's always a compromise." -Wikipedia

Added (3). Also I don't know why people down rated Krzy, looking at the reviews he seems to be right. The Sigma has generally positive reviews but more flawed units people received. Granted that doesn't make my decision any easier.

Added (4). And may as well comment on Taylor's answer since I already did for everyone else. The color quality is the main reason I'm seeing not to get the sigma since a higher aperture is very useful, yet you seem to be implying I should get the Nikon.

Maybe I'll just look for somewhere to rent both and compare.

Stop worrying about color - Color/tint of images can easily be changed in computer software. They're both nice lenses, but I would stick with the genuine Nikon, unless you absolutely need a maximum aperture of 2.8.

Hi

Nikon has better Quality Control than Sigma - when you buy a Sigma lens, you're more likely to buy not quite perfect lens. I think, that if you don't need f 2, 8 - Nikon lens will be definitely a better choice.

Depends what you are wanting the lens to do for you…

the colours aren't determined by the lens… But the camera…

Sigma lenses are good quality & for me, that constant f2.8 aperture throughout the range would be the deal breaker.

Edit: I meant that it would clinch the deal for me - the ability to have f2.8 throughout the range! I know it can be set higher! It means that you still have f2.8 ability at 50mm, whereas with the Nikon, your max aperture is going to be around f4-f5 at 50mm. I didn't say it was a bad thing - you misread my answer - in fact I meant the exact opposite!

Edit 2: By 'blown out' backgrounds I assume you mean shallow depth of field. 'Blown out' is a term usually used to refer to highlights which have lost detail.