As somebody who just switched from an iPhone to the Nexus 5X, the main things I found "greener" on the Android (in order of most to least important) that convinced me to switch were:
Cheaper. I got a used Nexus 5X 32GB for $300. If I wanted an iPhone, I would have had to spend $400 for last year's 16GB model.
Notifications. I couldn't stand how on iOS my notifications would disappear into the notification shade after unlocking my phone. Especially since there wasn't any indicator on the status bar of missed notifications.
A swype keyboard. The 3rd party keyboards on iOS sucked.
Having a file system and sharing capabilities between apps. I like how it functions more like a computer and that I don't have to jump through hoops to open certain files in certain apps or whatever. This also makes it really easy to set an mp3 as a ringtone or notification tone or alarm tone.
I thought I would miss iMessage, but have since switched to Telegram with my main contacts and must say that even if I did switch to iOS again, I would stick with Telegram. Especially since I don't have a Mac.
It's too soon to tell if I will miss the battery life and camera on iOS, but as of the past week, I haven't really noticed any disadvantages. The camera takes great pictures and the battery lasts me through the day.
OH there is one thing I noticed about Android. If I'm charging my phone while using it, it basically doesn't charge. It just doesn't go down...
I still think I was more efficient, such as unlocking my phone and opening up an app really quickly, on iOS. But that's probably just muscle memory that will come with time.
Overall, I'm happy with my new phone (and especially the price)!