The battery life of my iPhone 7 Plus is
insane. I'm coming from an iPhone 6S and previously I'd have to charge the phone twice a day. I've had my iPhone 7 Plus for over 24 hours now and it's still going after the initial charge - I'm actually on 43% to be precise. I'm honestly blown away by it. This was more than enough of a reason for me to upgrade; I now get 'extras' such as a faster phone, bigger screen size, better camera, water-proofing and much more!
Edit: for those curious, I'm a gamer (play heavy duty games like Vain Glory), watch Twitch for hours at a time whilst working, use Safari a lot, use Facebook a lot, Snapchat and what-not. I went to upload a screenshot, but for some reason the phone think it hasn't been fully charged yet - if that's the case, then wtf? I'm going to get even more battery usage?!