He should stick with Apple but if he wants Android, he should consider the next Pixel. The S8 despite the hardware is just not as fast or smooth as an iPhone 7, it's a fact and it will most likely slow down the line. Every single person I know who has an S7, lags or stutters to some degree.
I've owned the Galaxy S, Desire HD, One M8, Nexus 7 2012 and 2013, Z3C and Z3, used the S7 and S8, none of them beat the equivalent iPhone's performance. You can do more on Android but if you actually use apps or play games rather than stare at the homescreen, iPhone is better. The iPhone may not do as much as a Galaxy but what it does, it does better.
Surely you'd rather have better quality apps and more choice than change icons of the homescreen or font of the OS. Eg, Shazam didn't even get the auto feature until recently yet iOS had it for several years, there was also the issue of Instagram photos being of lower quality on Android. Little things like scrolling to the top instantly, swiping left to go to the previous screen or Force Touch do really make using iOS better.
I don't buy into any of that and it's not something you can prove from just trying a few apps, some apps are better, some worse and some more or less the same, all depends what apps you regularly use.
It's the same rubbish iPhone users has been spouting for years.