I'm another who just recently moved from WP to iOS. It was pretty difficult to let go. I went from af Lumia 920 to the 6s Plus. There were several things that were pretty annoying to get used to that just worked wonderfully on the iPhone. Simple things like just editing text with a tap and getting suggestions that were you wanted to replace it with vs having to tap short hold to select and getting lackluster suggestions on iOS. LOVED Quiet Hours. This was one thing that I'll severely miss. Sure iPhones have the little cool switch to go between quiet and on, but having that automatic based on my work schedule was awesome, not to mention all the compliments I got from others who got the automatic reply before I even read the message; they thought that was always awesome because it was pretty smart for a device to do. That segues into Driving Mode. Driving Mode is awesome, on how well it works when you pair it with Bluetooth in your car, this impressed many others as well. But it's flawed in how you cannot manually turn it on without having it to pair to Bluetooth. If it was paired with Bluetooth anyways couldn't you just use Cortana to do hands free interactions? Kinda was stupid how it was implemented (would have made more sense to be able to start this manually, or use NFC to trigger it with stickers). Glance.... oh how that was another thing that was difficult to let go of. Glance made LED notificaitons seem archaic, and going to iOS without glance was hard, but mitigated for the most part because I have a Microsoft band that alerts me anyways, but for my father, he really misses glance, and is considering just testing his 6S+ for 10 days before deciding. From Glance we have Tap to Wake. No idea how useful this is and how much of a habit it becomes. After this was the super sensitive screen. So sensitive that I use my pen (Pentel Energel Alloy) as a stylus. Who needs a Note 6 like device when you could use a metal pen or object as a stylus already? Because of that, shapewriter became even more amazing. Being able to use my pen to do shapewriting was really nice when I had my Lumia 920 on the table. Didn't have to pick it up, just double tapped with the pen and shapewrote replies so easily and so quickly. Another area was nonphysical buttons. I've seen so many iPhones with busted home buttons, you'd never have that on Lumias due to use of capacitative buttons (I've been afraid of over using my home button on my 6S+). Oh, another thing are offline maps. On iOS if I use the native maps app I worry about how much data is being consumers, but you know, there's an app for that, so I downloaded Here Maps, and for some odd reason it speaks super fast, but at least I have offline maps? I still haven't been able to find a GPS app that was as feature packed as it was on WP8 with offline maps. Then there's the obvious things like Live Tiles, replying from the notification center (W10), etc.
Now things you gain with iOS (the things that keep me from going back). TouchID is almost as habit forming if not better than tap to wake. App Quality is better for key apps (Facebook, etc are amazing, then you have things like Costco which are literally supped up webapps). Small details, like the detail pane in messages that let you review all the attachments is super nice. Apps. I finally have all the medical apps I need as a pharmacist (this is probably the deal breaker for me to go back because its important for my career.). Airdrop. Airdrop is amazing. I thought I'd miss being able to tap to send, but geeze, airdrop is so much easier. Just have ppl have it turned on contacts only , and you'll be able to send things super quick instead of having to have to tap to send. Future proofing. I think iOS and Apple products in general are the most secure for future proofing. The iPhone4s was even updated. But the conundrum is quite a few of Apple users are the type that have to upgrade every year. If you find to be that type, then you negate this. I got the iPhone 6S+ for the ecosystem. With the iPad Pro giving newer tools to use with apps, the Apple TV giving better access to the bigger screen, and iPhones for mobile, you can see how strongly supported the ecosystem is. You know Apple isn't going to just start ripping things out (like Microsoft did with hubs, then Skype for W8, then Photo apps for WP8). Something that trigger this thought for me when I switched was seeing the plethora of bands they have for the Apple Watch. They continue to strongly support that platform as well. Then there's lots of other things like how amazing panoramas are taken, slo-mo video for the laughs, etc.
Imo iOS is just worth going to now even though WP, I think, is a better OS. You have much more quality key apps (not all apps are better, still can't find a single app that is close to Tango Master on WP), support, key features that are solid (details pane in message, panoramas, etc).
Anyways that was probably a small snippet into what I went through. If Microsoft apps were just as good quality as they are on iOS, I might not have moved, but that sort of thing signals to me that Microsoft is has iOS as a higher priority. The best Windows Phone probably is the "iPhone Pro."
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