iPhone 5S is a great, fast phone. Remember, say 53 weeks ago it was still the current and best iPhone for sale. I actually gave one to family this past January. I use mine as an iPod in the evenings, and I like that size for use as a bedside iPod.
Honestly, I had mine out tonight doing a speed test, so I had it in more light, and it is one sharp looking phone too. Yes, it has a small screen, but it is a beautiful design and offers strong performance. I'm not surprised there are some people who prefer it to the iPhone 6.