I had the iPhone 5 for nearly two years now, didn't upgrade to 5s, so TouchID device would be a nice upgrade. Also, bigger screen which iPhone 5S should have featured when it was launched. Also the both cameras are better, front and back, and I love to take photos and videos. I have all professional Canon gear for that, too, but sometimes is nice to have a small camera handy, so iPhone 6 does that brilliantly. The NFC / Apple Pay is also a nice addition, very easy to use once it will be adopted everywhere next year, rather than carrying 3 debit cards with me, just use the phone to pay.
You can add to that:
- better battery power
- higher resolution screen
- dust proof and water resistant
- notably faster downloads
- bigger screen size
- thinner
- has manual exposure