They cover completely different angles of view, so I don't think it really makes much sense to compare them. To illustrate:


The 17-85 on a cropper is equivalent to 28-135 f/5.6-9 on full frame.


The 28-135 on a cropper is equivalent to 45-216 f/5.6-9 on full frame.


28-135 is very different from 45-216.


In any case, if you compare the parts where they overlap (28-85), the 17-85 beats the 28-135 by a wide margin in contrast and resolution.