If you are not using an upgrade discount to purchase your One, it is definitely a better option to buy the unlocked version from HTC. the unlocked version is cheaper than the AT&T phone with off contract pricing. And yes, the unlocked version will be updated much quicker than the carrier models.
so if I get the unlocked one and put in a AT&T sim card will it work fully as in 4glte and hspa+ and will be able to install some of the at&t apps
Sent from my HTC One using Android Central Forums
AT&T is slow about pushing out upgrades/updates. I will not hold my breath that it will happen soon.