After having the opportunity to build a few sets of ATA and AP armor I just wanted to point out a few differences between the two, I always thought they were about the same size, this may help some with deciding on which to purchase.
Major differences are the helmet size, AP is slightly smaller, secondly the chest back plate circumference, if you use the minimum cut lines AP is 2 inches smaller on each side compared to ATA, makes a huge difference if you have a light belly, made it really hard with one set that was pre trimmed, shims needed to be added on AP but not on ATA.
I also noticed the detailing around the ridges on the thighs are not as prominent on the AP armor.
Just my observations, take with a grain of salt