I have heard differences on these, Apple store says ATT for brazil and such yet this is the one with less bands, which is the better phone for all around international calling and LTE
Last year the AT&T was the "best" in that it was the only one that supported Band 30. Now with the iPhone 7 it is back to the Verizon/Sprint version.I assumed Verizon is always the best one to get. However this year was surprised to hear the Apple rep say "every year there is one that's better then the others this year it's att T-Mobile"
According to the T-mobile website, the iPhone 7 they sell (same as AT & T model) will not work in Korea.The only countries in the world which use CDMA are the US, Japan, and South Korea (with growing GSM). The rest of the world uses GSM exclusively. So, depending where your travels take you, you may be fine with just the AT&T or T-Mobile varieties (they are identical GSM-only models), or would want the Verizon/Sprint ones which have GSM but also CDMA. The LTE bands on both are identical, and having only GSM will not be a detriment in 99% of the planet. CDMA is a technology which should have been drawn and quartered 20 years ago.
According to the T-mobile website, the iPhone 7 they sell (same as AT & T model) will not work in Korea.