For me my Apple Watch and corporate emails are keeping me on iOS. I know a lot of people hate the AW, but I love my and have spend way to much money on bands. I honestly would not want to move back to android for that reason alone. I have used an Android Wear watch as well, but I really like the AW better. Just me though. Nothing against android wear at all.
The biggest thing though is my work email. It works much better with the iOS stock mail app, and I don't have to agree to let my company take over my phone if they need to on iOS. I don't like the message they give me on android that they can deactivate and wipe my phone at any point. Maybe this is more of my company thing this iOS vs android, but email is a very important part of my work life, so I need it to work flawlessly.
Again I have nothing against android, and would love to give it a try from time to time, but those to things plus having so much Apple stuff in my house keep me with Apple.
I have a AW and a Huawai Android watch, so I have always loved going between the 2, I figure Ill keep my 6 Plus so if I have a day where I miss my AW I can slip the SIM Card into the iPhone and use it for a few days