I have used both extensively. In my opinion, AN40 is much more supple, castable and has less memory. Yo-Zuri is much stronger, abrasion resistant, more sensitive and less stretch.
I suppose if you compare the actual breaking strength of the two fairly (and not the stated # test), the Yo-zuri would possibly overtake the AN40 in all categories. For example, the YZ #6 breaks at 11.9 lbs. The AN40 #6 is probably closer to 8lbs which is equivalent to the YZ #4.