Does lens performance vary by camera (28-75 on XTi vs on T2i)

I have $600 to spend and am trying to decide between a wide zoom and a medium zoom and am looking at the Tamron 17-50 non-VC and Sigma 17-50 OS HSM vs. Tamron 28-75 and Sigma 24-70 in that price range

I like to shoot portraits and it would seem like the 28-75 would be the way to go... but I had this lens when I had my first digital camera, an XTi. I did not like the results I got at that time (color cast, out of focus) and traded it in for a Canon 28-135 which was OK.

A few years later I've upgraded to a T2i and my skills have improved. I looked back through the photos and notice they seem noisy and the color cast is awful. I blamed the lens at the time... could it have been operator error and possibly the camera?

Is it worth trying this lens again or should I consider the much larger and less walk around friendly Sigma 24-70?
Would one of the 17-50s work OK for portraits with 2.8?

Newer cameras have more pixels and other bells and whistles that may help you get better shots. But, a lens is a lens.

I had the 28-75 on my XTi before I got the 5D MkII and loved it. Although it is a little short on the wide end, if the focal length suits your purposes, then by all means get it again.

I've never really noticed any of the problems mentioned; color casts are rare the lenses fault (maybe WB?) and noise is definitely the camera's fault (unless the aperture isn't giving you enough light)