It really depends on what you like AND what you don't like. What are your dailies?
For me, FaceTime just doesn't work. I wear a combo of glasses and contacts. I'm not going to base my glasses on whether software can detect them. Also, my phone sits in my bag a lot and I want my phone unlocked when I glance at it. I know there are plenty of smartwatches that can connect to the iPhone, but from what I hear, your mileage can vary since they aren't as deeply integrated. Unfortunately, I don't like the way the their watch looks. TicWatch, M. Kors and Fossil for me.
I live in notifications-my bar makes my daughter shudder and I like the way I can interact with Google's better.
Last, NOTHING beats call screening. It has changed my life.
Looking over this, I guess for me, it's more about the software. You should base it on how you use your phone.