As an owner of an s8+ and an iPhone 7+, I'll provide some feedback on the shortcomings here:
-lack of file system isn't a big deal for me since everything goes on cloud services such as Google photos, dropbox etc. I very rarely found myself facing a task that would be possible on Android and not achievable on iOS. Some tasks get accomplished faster on iOS, others faster on Android.
-biggest shortcoming is the screen and large bezels on iPhones. The screen, despite color accuracy, the display looks ancient next to the beautiful amoled displays that high end Androids use. After getting used to a Samsung display, the iPhone display is rough on the eyes. So washed out and blurry text.
-storage. Nothing beats expandable storage and you will not find this on an iPhone. However, if you use cloud services this may not be that big a deal.
-huge bezels and heavy weight. The 7+ is massive and a pain to hold. I have to use it without a case because with a case it's difficult to handle. This won't be solved with the release of the iPhone 8 since that display is going to be more towards the size of the s8 not the s8+. I'm willing to bet that there will be an 8s+ or iPhone 9+ next year so there will be one less shortcoming next year most likely.
-low light camera. I love the 7+ camera but not at night. It suffers badly with night time shots.
-multitasking. There is no split screen multitasking on the iPhone. Only on iPad. That's a major con for many people.
-customization. Android's openness allows for customizing every little detail vs iPhone where it's not possible and force you into it's archaic but clean and user friendly interface.
-notifications. I am one of the very few that prefers iOS notifications, but most people prefer the way Android handles them. I prefer the individual details and the ability to scroll down to see all your email notifications and raise to wake is awesome but most people prefer Android because every app notifications is on one screen.
There are a lot more shortcomings but these are the main ones I can think of. There are many other little features that are not found on iOS but the ones I mentioned are the ones that users notice the most. All in all I prefer the s8+, the difference maker is the form factor and inferior display of the 7+ which keeps me using the s8+ as my daily driver.