My 6S Plus is the fastest phone I've ever owned, when it comes to UI. It's a pleasure to interact with.
When compared to my Note 7, it's also significantly bigger, with smaller, inferior screen, and a litany of little and big things that make the Note 7 a better phone. Once you get past the petty fanboism and spend some time with both, it's not hard to see why Apple's been trying to play catch up lately instead of the other way around.
Say what you want about Samsung (and they do deserve a lot of crap), but they keep trying new ideas, and keep improving them. They single-handedly invented the phablet market. The pen has become a great feature, the edge screen went from a gimmick to actually very usable on the Note, etc.
I think Apple has a Harley problem. They have built their ecosystem around a userbase that likes simplicity and stability of design over everything else. While that's great in the short run, it puts you at a disadvantage if you want to maintain relevance long-term. I'm sure part of the problem is that you have a supply chain specialist instead of a visionary running the company.
I have high hopes for iPhone 8. Hopefully Apple can take back the design crown and build a device that is truly exciting, not just another iteration of the same old, with removed features...