Years ago I couldn't decide which one.
So I bought an iPhone 4S and a Galaxy S4. The iPhone was my personal and the S4 was my business phone.
I tested both of them extensively for various things.
MrWizard hit many good points, I'll add my own experience.
I found the iPhone so totally proprietary that it would frustrate me to no end trying to do simple tasks. Apple dictates that you MUST do it their way and only their way. You MUST have iTunes, like it or not. With the iPhone, transferring pictures and such is a real chore. iTunes only.
Built in battery, have to get Apple to change it. Built in memory, can't expand it and so on.
Don't get me wrong, iPhones are an awesome well made device. They are reliable and they work well. It's just that every time you sneeze, Apple wants to wipe your nose for you with iTunes because they think you are incapable and incompetent to do it yourself.
Somewhere along the road I upgraded the 4S to a 5S with the same results. Way too proprietary to be user friendly.
With my Samsung Galaxy S4, I never had a moment of trouble. Like the Apple products, very good quality and reliable.
But with my Android device, everything is so much more user friendly. If you want to transfer pictures, files, anything, just USB cable it to anything, drag and drop or send files any other way to another device, done! Or pop out the micro SD card and plug it in to something else. Simple, easy, no headaches. S4 had a removable battery too. My S7 Edge doesn't. But I can toss my S7 in a swimming pool, dive down and get it with no harm done. That's why the battery is built in because they made it waterproof to a certain point.
Want more memory? Plug in a micro SD card, done!
Bottom line is they are both good devices. Lots of good reasons here to go one way or the other, depending on your own personal needs.
I have a 4th gen iPad too. Getting kinda old but it's an awesome device. 4th gen? 2nd gen? I forget, its from 11 or 12....
Almost 2 years ago, after using both Apple and Android side by side, I divorced Apple for the reasons stated. I bought my S7 Edge and a Galaxy Tab3 tablet.
The iPhone was in perfect condition. I gave it away to an elderly lady who needed a cell phone.
The S4 I just gave away on this forum a couple weeks ago. The iPad still sits here. I use it occasionally because one of my email accounts is still on it.
I personally prefer Android devices, specifically the Samsung Galaxy series. They work seamlessly together and I can bluetooth them to anything with ease, move music, photos, files around in moments without Android dictating to me to load some bloated invasive program like iTunes to harass and haunt me every time I blink.
But here is one for Apple - even at about 6 years old, the battery in my ipad is way better and lasts a lot longer than the ones in my 2 Galaxy devices.