15-85 vs 18-135 comparison shots - what's your opinion?

Hello,

I just got the 15-85 I've ordered and took some comparison shots with the 18-135. Do you think it is really as sharp as it should be?

It has no lens creep. But with comparison to my 18-135 (especially the last shot, see the bush) it seems less sharp.. what's your opinion on this? shall I return this copy of the 15-85 and try to get another one? or more testing first? (i've a few days left before returning it)

I did shoot all of the pics hand-held by focusing on the yellow plate in the middle using AF.

The entire pic:

top-right corner:

bottom-left corner:

100% zoom of the center:

Thanks for your suggestions!