i wish you could pick mine up!
look on B&H, its cheaper. And it seems as if both will work on the 40, its just that the APO version is newer obviously, and it seems that it will be a little quieter, faster, and cleaner looking (picture quality wise)...
scroll down just a little bit, read the title and you'll see which ones are for Nikon.
http://www.bhphotovideo.com/bnh/cont....y=0&Go=submit