I've had Android tablets - Nexus 7 (2014), Samsung Tab Pro, Samsung Tab S2... I was less than impressed. The Nexus 7 was probably the best --- ASOP Android ftw. I used that for years, even played Ingress with it for a long time (with a hotspot) (San Diego Anomaly).
Don't get me started on the Samsung tablets.... I will NEVER EVER EVER do one of those damned things EVER again.
Tab Pro was gifted to me for ... FREE. At first I wondered why. Didn't take long to realize why. Damn thing wouldn't charge half the time and restarted like crazy. It NEVER got an update from Samsung even though the original owner paid $500+ for it and Samsung promised it would be an iPad replacement. So I rooted it but after awhile the battery kept requiring disconnecting from the board to charge and ... then it stopped charging no matter what I did.
The S2 wasn't TERRIBLY BAD but it sure was bad. I paid $350? for it. It had its weird quirks that made it very unpleasant to use. The screen was just terrible, absolutely terrible. Battery life would randomly drain one day to the next for no reason... Apps crashed left and right. I had a Samsung update that kept forcing me to install it - it would crash and tell me I had to go visit a Samsung Service Center - then download the update again and force me to install it again. This went on for 4 months - tried tons of ways to fix (no, resetting tablet didn't help) and eventually found an obscure post showing how to fix it (a misplaced file). It was so bad I gave it away to a family member for free because they had broken their phone and didn't have a replacement (better than nothing, right?).
iPad? The iPad screen is FAR sharper, far more pleasant to read on for hours, battery life lasts me a week easy... I can set it down for DAYS and it will be within 5% of where I left it off, the apps for iPad are far superior... iOS is just so much more pleasant to use. This is on a huge scale I can't stress it enough.
Some other points that members above mentioned... I can iMessage with my iPad, answer calls with my iPad, and access all the apps that my iPhone has. But mostly, I use my iPad as a laptop replacement with my many bluetooth keyboards around and recently, as my TV (youtube red!).
It's really no contest to me. And this is coming from someone who prefers Google to Apple.