I have a D60 with very cheap Sigma 28-135 and am not happy with the results off this lens. I am considering upgrading to a Canon 24-85 or 24-70L but am not sure whether the 24-70L is worth the higher cost in terms of picture quality.
I would be grateful to hear any advice before I make my decision.
IMHO, it depends on how you want to use the lenses. I have both. For example, when working shooting weddings or portraits, I ALWAYS use the 24-70. Faster, shaper, simply a much better lens (as it should be).
However, as my general walk around lens, I use the 24-85. Much lighter. Still a nice lens with good contrast and sharpness. USM. Much, much less $$.
The 24-70L is a zoom lens with no compromises. Go for it if you want the best zoom in this range, and if you can bear it. It is big and it is expensive. To me a 24-85 wouldn't be an alternative since you already own a lens in the 28-135 range. If you want alternatives to the 24-70L study some reviews of primes. A 50/1.4, a 24mm/2.8 or a 100mm or 135mm are great and compact at the same time. Be warned, once you buy primes you're lost. Zooms will always look as a compromise to your eyes.
