I wonder if, in real world use, Samsung's skin/bloat is better now than it used to be. People seem to say that it is. I have an Nexus phone running stock Android and the experience is terrific, but I haven't used a Galaxy S7 or S8 day-to-day. I do ponder whether the S8 will slow down after six plus months of use.
Interesting to hear your thoughts on the iPhone, seeing that you were originally an Android guy/gal. I haven't been satisfied with iOS since iOS 6. Call me one of those guys "living in the past," if you want, but that was the last bug-free version of iOS that I used. I've encountered numerous visual glitches and bugs from iOS 7 on, and so in my personal experience, I don't find iOS that much smoother than Android. Perhaps no smoother at all. Perhaps I'm holding the iPhone to too high of a standard, as iOS is much more advanced now than it was years ago. With more features come more chances of bugs.
I agree on the Mac integration and Apple Pay performance (I haven't ever used Apple Pay myself, but many here seem to be very pleased with it). Apple's closed system definitely plays to their advantage in those scenarios.