I compared an 8 Plus to my wife's 6s (non-plus). There was little perceptible difference in speed when navigating around iOS generally. Heavier hitting apps l

I compared an 8 Plus to my wife's 6s (non-plus). There was little perceptible difference in speed when navigating around iOS generally. Heavier hitting apps loaded faster, but not noticeably so. Slack behaved exactly the same, even scrolling through long histories. I ended up getting an iPhone SE to save money ($175 credit for my iPhone 6 Plus helped). It's a 6s with a lesser camera, 4" screen. Runs smooth as butter.