I've had all the Iphones and 7 has a good battery, better camera and the speaker sounds nice. The 6 was good except for the fact that is wasn't water resistant and the screen would black out once in a blue. Kinda blink.
I needed a die-hard cover for the 7 and the T-Mobile store gave me the Lifeproof Fre (Free). This cover lets you go under water, drop it, throw it ...it's great. I do not feel secure without it on the phone. They guarantee anything happens to the phone, they replace it...nice :)