Joshua, I'm not a gear head but I have found a particular website very helpful when it comes to evaluating corner-to-corner sharpness of lenses across various focal lengths and apertures. I looked up the two evaluations provided below and they indicate to me that the 16-85 and the 18-105 are reasonably comparable across all common combinations of focal length and aperture. The 16-85 loses out only at about 70 - 85mm but only when using a very small aperture, such as about f/32. You won't use that aperture often and even if you do, the difference in sharpness is not enough reason to go with the 18-105 in my mind when taking into account all of your considerations.
16-85:
http://slrgear.com/reviews/showprodu...ct/1177/cat/13
18-105:
http://www.slrgear.com/reviews/showp...ct/1221/cat/13
Once you read the reviews of each lens, click the Blur Index graph. A new window will be displayed that allows you to change the aperture and focal length.
Hope this helps!