Any reason not to get Unlocked and SIM-free iPhone?

[sekker]

space-time wrote:
it used to be that ATT had one more LTE band compared to T-Mobile phones, or something like that, so it used to be an advantage to buy an ATT. back the unlocked and T-Mobile lacked that LTE band. Also there was confusion about LTE bands in US and abroad, apparently one phone was better in US, the other was better abroad.

I'm hoping Apple is just selling one good phone, but I'd be ok with this being a good international device for my portfolio.