Why the app is faster is you get the work done in advance instead of standing at a Kiosk, you can do all the work on the plane within 4 hours of hitting immigration. Never had an issue with Kiosk availability for GE, but getting the passport read, finger prints done and answering questions slows you down. Plus if traveling with the family you just do the APP once where all have to stop and do the GE.

With 2 travelers you can time compare, one do GE the other do the APP. Other huge plus is you don't have the hassle of doing GE, which is huge when you don't live in a gateway city.