I wonder if there is an actually difference between USPS priority and Air Parcel Register. You get a different type of tracking number. My ROT66’s orders were USPS priority and both got here in under two weeks. I was checking out for an Astrolux MF01s last night, went back to change the color, and ended up with Air Parcel Register. I’m kicking myself for it now.
Two orders from a month ago, an Air Parcel and a USPS priority, seem to be showing up within a few days of eachother, so it probably is trivial. Even if it only meant better tracking, that would be significant.