I have been with at&t since the days of McCaw Cellular and after 28 years and many incarnations I am considering moving my Wife and I to T-Mobile as we are pretty sick of at&t at this point.

Colleagues have said that T-Mobile's network is inferior to at&t and that does have me worried, but the latest at&t billing fiasco also has me worried so I find myself looking for greener (or at least seemingly greener) pastures.

I have a Nexus 6 and my Wife has a iPhone 6 Plus (bought unlocked from the Apple Store) and from my understanding both should work on T-Mobile without issue.

The Wi-Fi calling thing is a little confusing and I have gotten conflicting info from both T-Mobile employees and the internet itself. According to the T-Mobile Corporate Store Employee, since my wife had her at&t SIM in the phone, the phone has programmed itself to work most efficiently on at&t and things like Wi-FI calling would be impossible, but other things like cellular service would be fine. The T-Mobile Employee told me that my Nexus 6 would just, "barely work with T-Mobile and that I really should get a better more compatible phone."

According to the Internet the iPhone 6 Plus would just work and whatever programming it had for at&t it would reprogram itself for T-Mobile. With regards to my Nexus 6, the Internet seems to feel that my Nexus 6 would work well enough, if not perfectly and that anything it might not be able to do, I really wouldn't miss. I tend to believe the Internet (in this case) over the T-Mobile employee as it seemed he wanted to make a sale rather actually assist us.

Any thoughts, before I make the change?