Originally Posted by WIRunner

Are you talking domestic or international? The Verizon and T-Mobile iPhone 6s is the same model, has the same bands. T-Mobile is fairly good about doing an unlock for you after 40 days of continuous use if you need a SIM unlock. (Their international rates are also fairly inexpensive as it is.)

If you're going to get the 6, the Sprint/US Cellular version is the one that you want, as it is used by the largest number of carriers.

For the SE you'll want the... well, the not-Sprint one has the most domestic bands, but the Sprint one is used most outside of the US.

An iPhone is extremely easy to unlock once the carrier authorises the unlock. Basically you just need to plug it into iTunes and it will do its thing. Probably going to have to do a restart. When I changed from USCC to T-MObile, I sent in the request and a week later I synced the phone and it was done. Put in my T-Mo sim card, it pulled a carrier update and that was that.

If you're with Verizon now, and thinking T-Mobile down the road, just get the Verizon one now. If you're going to port to T-Mobile now, then get the T-Mobile one and in September request a SIM unlock. (You should be able to do this via even Facebook or Twitter.)