I've owned both and while I give the edge to the 16-85 in image quality, that aspect of these lenses is actually pretty close. The 16-85 is of course wider and the 18-105 longer so which is better for you depends on your shooting habits.
The real difference between these, and a big part of what you pay for, is build/features. 16-85 has a metal lens mount, M/A focus mode, and focus distance scale (and the lack of the last one on the 18-105 makes it a really poor choice for all kinds of night photography).
Does that make the 16-85 worth the extra money? IMO yes but these differences may not matter as much to you.