The tipping point on swapping the 6S+ for the S8+ was the totally degraded battery life on 10.3.2
I had an S7 Edge, and I just got an S8+ about a week ago. My S7 Edge had marginal battery life at best, but with the S8+ I can't kill it! I'm getting spoiled running hard all day with the hotspot on some of the time and it being at 30 - 40% at bedtime.
I don't use an iPhone, but I have an iPad. I just switched from an iPad Mini 4 to a 2017 iPad. I have been very impressed with their battery life. But I know that tablets are a whole different ball game. I think the worst tablet I ever had for battery life was the Surface 3.