No matter which one you buy, if you are paying for it outright then it will be unlocked. You can use it on AT&T or pop in another SIM from a different carrier whenever you would like. It is frustrating that Apple is requiring you to enter in your account info for most of these, but if you choose T-Mobile it will be a GSM phone that will work on AT&T and all GSM networks and you don't have to put in any account info.Do I have to hire a consultant for all this? I'm on AT&T with Grandfathered Unlimited Data Plan that I want to preserve. But I'm going to be traveling and if in a non-AT&T area - want to be able to use another service for a few weeks. It seems I cannot do this. No matter what "Payment Method" I choose. Even pure full price unlocked phone requires a carrier tied to it and a phone number attached to that carrier.
Maybe I'm just damn ignorant - but I don't get it.
What we are all complaining about is that we want the Verizon version which not only works on all GSM networks but also on the CDMA networks (Verizon and Sprint) and that one you can't currently buy without providing account info.
Supposedly you can go into the Apple Store starting on September 16th and buy a Verizon "device only" which will be the most versatile GSM and CDMA phone but won't come with a SIM card. This hasn't been confirmed yet. It is also rumored that Apple will start selling a "SIM-free" phone on-line sometime in a few weeks, but again, this is just rumors.
For the vast majority of world networks (including AT&T), the GSM (T-Mobile) iPhone 7 will work fine.
The other speculation is regarding the modem that is used in these two different variants. The CDMA phone is believed to have a Qualcomm modem where the GSM is said to have an Intel modem. There is also speculation that the Qualcomm modem is faster and potentially capable of 4x4 MIMO (which T-Mobile is rolling out) where the Intel modem is not advertised as being capable of this. This depends on whether it is using the Qualcomm x12 or x10 though, so perhaps we're getting worried over nothing here. Also, I don't understand too much about this, but I've only heard that the Intel modem is "not advertised" as being capable. I suppose that doesn't necessarily mean it isn't capable.
All in all, everyone wishes we could buy a Verizon phone without providing account info because it is more versatile, and probably the superior version. I have settled on buying the T-Mobile phone because I am currently with a GSM network (T-Mobile) and I probably won't be switching to Verizon, so it probably doesn't make a difference. I also can't imagine that 4x4 MIMO will work on T-Mobile's network using the Verizon iPhone 7 but not the T-Mobile iPhone 7. That would just be ridiculous. I imagine they would rather not allow it to work at all rather than make it work only on phones that were bought to be used on competing networks.
I've personally decided I'm putting too much thought and worry into this and if I decide to switch to Verizon in the next year then I will cross that bridge when I get there. For the most part, people are moving away from Verizon anyways due to their high costs compared to companies like T-Mobile.
If you're with AT&T and you don't want to provide your account info to Apple, then just buy the T-Mobile version. You will definitely be able to use AT&T and use another service for a few weeks if you're travelling to a non-AT&T area. Just buy a local sim, swap them out, and you're good to go.