Which samsung galaxy S6 will work properly in the US? The G920i or G920F

[AC Question]

Looking at unlocked GSM, for Consumer Cellular, which uses ATT coverage.

 

[Rukbat]

I know many people are using an unlocked F on AT&T. (According to the local AT&T store manager, they're activating more Fs than As on most Samsungs recently. People REALLY don't like the locked bootloader on the A.)