Canon 17-85mm f4-5.6 - Sell or get a new lens ?

ItsMeta wrote:

A used 15-85mm may be a good option for you...

The 15-85mm would seem to fit due to it's focal length, but it's lacking the quietness and quickness from the auto focus. Coming from a USM lens, this can be quiet bothering to me.

15-85mm is a USM lens. CA, distortion and sharpness are all much better than the 17-85, which is quite a pedestrian lens in those areas.

The 18-135 STM as suggested should also be good...it's very sharp, and the STM motors are incredibly quiet (exception being 40mm f/2.8 STM prime).

Another priority I forgot to mention when I was listing out what I need in a lens, is it's resale value. I really wouldn't prefer a good lens with a horrible resale value (As I plan to be able to sell the lens if I want to upgrade in the future).

That's something you'll unfortunately take a hit on with EF-S lenses. The good ones (17-55/2.8, 15-85) have decent resale, but not in the same league as the L lenses.

I thinking of getting the Sigma 17-70mm or the Canon 17-40mm L as I heard great things about them. I'm not completely sure about the resale value of these lens, so does anyone happen to know ?

The 17-40mm is a bit of a silly range on crop...if you're used to the length of the 17-85, the 17-40 will be severely lacking on the long end for reach. It has good IQ on a crop, but also keep in mind it lacks IS.

Sigma 17-70 is a decent lens, but resale will be mediocre at best. Also note that Sigma lenses may need detailed AF adjustment to work properly on some bodies.

A key draw for the Sigma is the fact that it's 2/3rd stop faster on the wide end than either the 15-85 or 18-135 (f/2.8 instead of f/3.5), and a stop faster on the long end vs the 17-85 and 15-85 (f/4 rather than f/5.6)