Good question. Though, usually threads like this bring out a lot of hostility from both sides...
Short Version: I prefer iOS because I don't have time anymore to spend rooting a phone to get rid of gigs of adware that report my every move, action, choice to random ad servers at home. I like the superior build quality of Apple devices and the fact that out of the box, they run fairly well. I used to be a HUGE Google fan, rooting android phones and very anti-Apple. But when I tried my first iPhone, it changed me completely. That, along with the fact that I met a girl I fell in love with, got married, and started working a job that required more time... Apple devices impressed me for build quality, stability, and apps that worked a heck of a lot better than Android apps. Every year I try out a friend's Android phone for a week just to make sure I'm being fair to both platforms, but I definitely prefer Apple.
That and I've fallen out of favor with Google. I try not to use Google products or Google apps if I can. In this age where privacy is non-existent, I've moved to FastMail, Safari, iCloud, etc... Having actually looked at code in Android roms that were being rooted, seeing what apps like Facebook did back in the day - I value my privacy more these days than I used to.
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Long Version:
I started out with Android with an HTC MyTouch on T-Mobile. Being someone who builds computers and works tech, I quickly got into the Android rooting experience. When I got the Droid 1 I was beta testing roms, installing different roms every week, and spent countless hours on DroidForums helping others root. I was very anti-apple back then, but I had never tried it. Pete's Bugless Beast was my favorite rom on the OG Droid. I went from the Droid 1 to the HTC Thunderbolt (4G LTE) continuing my Android "love" - but rooting was getting more and more difficult.
I went with a coworker to get an iPhone 4s because he was very pro Apple and I wanted to see what it was like. I was VERY impressed by the 4s. Loved the way the phone felt in my hand, how the OS flew, everything was so pleasant to use I actually USED my phone. Apps were so perfect vs Android.
But I lapsed and went back to the Samsung Note 3 because I wanted a bigger phone. However, I was shocked to see the rooting world falling apart. I was part of the group that raised some $36,000? to hire a hacker to crack the locked bootloader so we could root our phones, but Verizon was making it more and more difficult - rom devs bled from Verizon to T-Mobile and eventually disappeared.
So, I went back to an iPhone 5 and stuck with Apple from the 5 to the 6+. The 6+ was the first Apple device I really fell in love with. The size, the battery life, the screen, everything - I loved it. It wasn't until I got the 6s+ that I started becoming anti-Google - their privacy practices and need to sell everything I do out to companies. Android flagship phones are hardly cheaper than iPhones yet they blast a lot of what you do to ad companies.
Now that I'm older, the ability to iMessage from ANY device, answer calls from ANY device, I just love the way text is rendered on a Mac vs Windows. Apps on Android just don't seem as polished as iOS. Airpods on ANY of my apple devices is just astounding. Always on the latest OS (I've bought 4 Samsung devices that were NEVER updated in the years I owned them).
My 8+ has cemented my opinion that I will be sticking with Apple for a long long time. I miss the days of rooting but, I've got more important things going on in my life at the moment.