iPhones are always better than the equivalent Android phone under identical usage. (There's no emulator to support.) And battery life will still depend on the signal strength of TMobile's signal where you go, not the strength of Verizon's signal, so the Verizon signal strength is no indicator.TMobile allows you to take a phone for a test drive. Run a signal strength app on your iPhone on Verizon and
LTE Discovery on the TMobile phone and see how the signal strengths compare where you go - your bedroom, at your desk at work (signals can vary if you move the phone a few inches, so the signal in the street in front of the building you work in won't tell you if the phone will even work at your desk). Then you'll have your answer about signal strength. (A TMobile phone won't search for a signal any more than a Verizon phone will. If there's a signal there, it finds it.)