At the beginning of this month I sold my Jet Black 256GB iPhone 7 Plus that I used for the past almost 4 months together with the Apple Watch I bought 2 or 3 months ago in preparation for the arrival of the S8. I consider myself an Android guy and have hated iOS limitations and restrictions since I remember, but being a tech freak I've had 4 or 5 iPhones in between my dozens of Androids, so I consider myself neutral enough to issue my opinion.
I had a Google Pixel and then a Google Pixel XL right before I got the iPhone 7 Plus and the Pixel was/is years ahead of any phone right now talking about smoothness, I mean, those ridiculous iphone Animations gets old really quick and then you appreciate a lot more what a phone like a Pixel really is and does, but man those huge bezels on the Pixels plus it is kind of boring after a while.
BUT, about the topic, my S8+ and a co-worker's S8 are as smooth as any recent phone I've had (including all the above mentioned plus, Axon 7, Note 7, HTC 10) and I can't honestly say it lags or stutters, but being honest and using somehow a similar analogy than was posted here before, I really couldn't care less if my S8 really opens a game 1 second later than an iPhone, I don't play games on it, but even if I do, are you really gonna tell me that opening games in real life where you open one game at a time not 5 or 6 of them, it really hurts to open it 1 second later? What about those same speed test videos where you are seeing the games opening faster on the iPhone, haven't you seen that most if not all the regular apps that most people use open faster on the S8 or at least at the same time than on the iPhone?
Let's do this, let me do a simple list here of a couple of things comparing both OS:
1-) What about the time you lose on an iPhone to simply closing all opened apps, one by one instead of just hitting the Close All button?
2-) The time you lose just by switching between the last 2 apps you opened, where you need to press and hold a button and then select it from the list, when in the S8 you just double press the recent apps button.
3-) When you need to open 2 or 3 apps at the same time looking for an information that you need, like in looking for info on a Browser while sending an email that will include that information on it, and you need to be switching between them the old boring and slow way, while on the S8, and now with Nougat, all the Android phones just need to activate the Multi-Windows features and have both of them opened at the same time.
4-) When you need to press at least 2 or 3 icons or buttons to take a picture and wait for the camera to open when you have n almost instant response double pressing the power button on the S8.
5-) When you need to open your phone just to see if you have a notification when you just need to see your LED light flashed or your AOD showing them.
6-) When you have 20 notifications all mixed up on your Notification area on the iOS and you need to go through all of them to find what you are looking for but just have Grouped notifications on your S8 (Android).
7-) When you need to look across all your Home screen's apps and/or folders to find your app's info when you can have even an updated widget wherever you please to have them with such.
When you need to scroll though all your Widgets in the Widgets panel to look for the one you want when you may easily have 3, 4 or 5 of them all together in your Main home Screen looking immediately at them.
9-) Limited Quick Toogles on iOS Vs Tons on S8 (Android in general).
On the hardware part now:
10-) When you need an absolute fast but good charge because you need to leave and you have no fast charging on your iPhone.
11-) When you need to connect your iPhone at night lying on your bed and need to basically get up on the bed to look for the cable and then if it's very dark be very cautious to not scratch your phone with the cable because you can't see the connection, while on the S8 you just basically drop it on your Wireless charger.
I think the above is more than enough even when I know I can think of a couple more of them to show you that maybe for gamers, that in a fantasy world can open and play 4 or 5 games at the same time, watching those ridiculous speed test videos can think that they make sense or are important, but for the real users, the ones that doesn't open 10 apps and games in a row to see how fast they are opened, Benchmarks and speed test don't matter, tools and great features are what is important, and in that category, plus being a gorgeous phone (best looking in my opinion), with the best display and one of the best if not the best camera available, the S8 shines and exceeds expectations.
People if you like iPhones better than Android, great, no shame on that, if you try the S8 and you can't deal with it giving it a fair try and yourself a chance to learn and get used to it and Android, then great, the iPhone is for you, it is a great phone, just not the best for me.