The answer, for the things you use every day, is "iOS is better", and I don't think it's close. I quit Windows Phone last summer and tried an Android phone first. It was an HTC One M8, not exactly the most modern. I use Outlook.com for mail/calendar/contacts, and trying to work with them on an Android phone was a disaster. Android wants you to use GMail. There is no other way to say it. If you are on something else, you are a second class citizen, and stuff just doesn't work. Do you like using OK Google to quickly schedule appointments? Good luck having that appointment show up on your non-GMail calendar. I couldn't edit contacts really at all.
If you ask me, Android offers the user *too much* control. Too many fundamental things you need an app to do, and you end up with competing apps doing similar things and not working well together.
In January, I gave up on Android and moved to an iPhone 6S Plus, pretty close to state-of-the-art in the iPhone world. Apple doesn't have a dog in the e-mail fight, so Outlook.com for mail/calendar/contacts is a first-class citizen. I can edit my contacts. Appointments I schedule with "Hey Siri" go right onto my Outlook.com calendar. I haven't bothered trying to use Cortana. I wish iOS were a little less locked-down at times (I think Windows Phone nailed the right balance of user configurability better than either alternative), but for things I do everyday, I am extremely happy with the iPhone 6S Plus.