going with the at&t variant. after using a galaxy s4 16gb model for a few months i realized that a 16gb phone with microsd card slot was more than enough storage for me. so at&t version being 16gb is a non-issue for me. also i have no allegiance to a specific wireless charging standard so at&t going with pma is a non-issue to me. plus the fact that i like at&t's service in the city that i live in and most of my family is on at&t leaves me with the at&t model.
Too late, but you think your 720 could handle the WP8.1 update, though?How about putting an option that says "None, happy with my current phone"?