Both have the same clone movement and are very well made. In the end it is down to your personal preference.Kinda feel foolish asking- but 54 pages and I am going back as much as I can and not sure if ZF or APSF is the one to get... I am going after the blue dial and might just go ahead with getting one from a TD to try out. If it does not work out, I can always offer it on the classifieds.
Although through my research looks like the 15510 was not updated, still has wrong bracelet which is a shame.
The 15510 also has a wrong hand(s)