1. copy and paste function is very flawed and unstable,
2. very weak email handling in stock Mail app for accounts of Exchange, Hotmail, Gmail,
3. Siri being much less efficient than Androids alternative Google Now,
4. iOS 9 being unstable during hectic work sessions,
5. YouTube app not being able to view video in 1080p or 4k quality,
6. not being able to open some websites in Safari,
7. 3rd party keyboard crushing often, like Swift Key app,
8. loosing important emails with attachments,
9. no physical return button, is often a challenge,
I use both platforms (work phone is a Moto X) so I do have some questions, suggestions, and overall comments to most of your points.
1. Do you utilize 3D touch for copy and paste? It's touch to explain in text if you don't and require an explanation but search some YouTube videos. As much as I've "hated on" 3D Touch before using it, I think it's a boon, especially for this particularly.
2. I won't contest this. Since I only use iOS for personal email it hasn't been an issue. I use Gmail for email but I dislike the App. I've set forwarding up in such a way that I read all of my gmail forwarded to an iCloud account (thus receiving push email) but it is still sent through gmail. My wife does use exchange through work though and haven't complained, though she has virtually always been an iOS person.
3. Hey Siri has been pretty good for me although I do find that there are a lot more "let me check the web" moments than just finding me an immediate answer. If I want to search the web I'll do that manually, thank you Siri! Lol.
4. Tough to judge because I don't know what you're doing. It's great for me on my 6s plus but was terrible on 6 plus. This is a case of hardware limitations (for my experiences). I'm not sure what you're doing with it. If juggling two apps, 3D Touch app switcher (and the new "go back to" button in the top left) are great. Took some getting used to but multitasking is just faster for me now. I still yearn for split screen, which I don't think is unreasonable on a plus.
5. 4K I wouldn't care about since I'm limited
To a 1080p screen. I don't notice an issue when playing videos (they seem great to me, but then I don't play all that many videos and how stay haven't looked into setting to see exactly what quality they're playing on). My son plays quite a few videos in car rides and an hour of hd video seems to take up about 500-700mb
6. Never really had an issue here, but this depends on what you're trying to open. Flash has basically been abandoned by nearly everyone at this point, so again, if have to know what you're working with.
7. I've heard this. Unsure what the cause is (iOS versus just third party being poorly written). I don't really care for third party keyboards anyhow so tough to comment further.
8. Again, tough to comment. How are you "losing" emails? I'll concede some attachments are limited, probably, but in still unsure how spent Hong would be lost?
9. This is, again, difficult to say. I've been on iOS for years, and think 9 with force touch is actually fantastic. I don't find myself missing a back button, especially this year. With iOS 9 I find myself feeling a bit like Windows versus OS X. It's a different way of getting around and multitasking, but I find it equally as good.