I have tested this between my S8 and 7plus 256gb. Although unscientific I find that I get more usable signal on my S8. While in the break room at work, I am am unable to use data on my 7plus or make a phone call while my S8 allows me to use Facebook/instagram/twitter and make calls. Having said that, that is a big deal to me. I too use Tmobile.
I have to keep mine on 3G. Verizon LTE and Apple not good. It's the Apple 7 plus antenna. Even Apple genius stated this
This is good to here because according to the history of Android and Samsung, their signal reception was never on par with Apple devices. That was one of those areas that Samsung needed to improve.