From what I read on xda, the one that has the most bands is the Chinese one, which is the 9200 model.
Having said that, the best way to determine this is to Google which LTE bands are supported by each variant, and then which LTE bands AT&T and, and pick the one with the most in common.
Also note that with most of the international variants, the phone will say you're on 4G when you're on US LTE networks, and H+ when you're on US 4G networks. It will never say LTE, but if you run speedtest on it when it's showing 4G next to another AT&T branded phone showing LTE, you'll see comparable signals.
In addition, US phones show a higher number of bars for regular signal strength than their international counterparts when their signal strengths are identical.
Hope that helps.
Posted via the Android Central App