My first iPhone was iPhone4. Was a massive improvement over Nokia N97 which was my first smartphone. When the home button became a little unresponsive, that became my excuse to get an iPhone 5.
Everything was generally ok with iPhone 5 except the screen was kind of small. Actually it was really small. Especially when browsing websites and sending emails.
So I decided to get a Note 2. However I heard news that Note 3 was around the corner so I waited and finally got a Note 3. The much larger screen was greatly appreciated when sending emails and web browsing and I found myself watching more Youtube videos, something I seldom did on iPhone 5 due to the small screen.
Sure the Note 3 is big and I often have trouble digging it out from my front pocket and putting it back in when I'm seated, but hey you can't have your cake and eat it too.
Took a bit of getting used to as iOS obviously looks and works differently from Android. But wasn't a major problem for me lah.
But as some have already noted, iOS is practically idiot proof and is very well integrated with the entire Apple eco-system. Which is perfect for me since I use an iMac at home anyways.
Upgrading from one iPhone to another is idiot proof. If I can do it, anyone can!

Have heard its much harder on Android. That is a big issue as I have the bad habit of changing phones ever so often.
Another thing I like about iPhone is it uses iTunes for everything. I can download an app or update for an app on my iMac which is very fast thanks to my 500Mbps connection at home. Then plug in my iPhone and viola! I can't do that with Play Store. I need to download on the Android phone itself which is obviously slower.
I guess I've been spoilt by how easily iTunes does everything for me. Literally. Download & update apps. Find new version of iOS. Add or remove MP3s, edit details of each MP3. Make back ups. Everything!!
I also like how easy it is to upload MP3s. Just drag from my desktop and drop in iTunes and viola. For Android I need to find the correct sub folder and drop it there. Also, iTunes allows me to change details such as name of singer & genre easily. For Android I can't do that off the fly. Prob need some utility I guess.
On the topic of MP3, for iOS I can arrange the songs in my order of preference in iTunes and when I play back on my iPhone, its in that same order. For Android, or at least for my Note 3, the songs are all in alpha order. Even within each playlist or genre its in alpha order. I can't arrange it in my own order. Not a major problem but yeah, its a bit of a nuisance at times.
Also I notice newer releases of iOS tend to work with most iPhones, even the older ones. Take iOS 7 for e.g. Its not just for iPhone 5S. Its also backward compatible with iPhone 5, 4S and 4.
Android phone makers like Samsung usually only release updated OS for their newest phones. I received the update for my Note 3 as its still their flagship phone. Once the Note 4 is out I'm pretty sure I'll have to wait forever, maybe even never, to get any more updates. Just like how slow or practically non-existent are the Android OS upgrades for older models like Galaxy S3 or Note 2.
So yeah looking forward to getting iPhone 6 and moving back to Apple. Was tempted to get the 4.7" as its easier to fit in my pocket but considering the resolution is lower and the battery has less juice, decided to get the 5.5" instead.