IMO, Eye AF is the best thing since sliced bread!
One of my main complaints about the Canon 6D Mark-2 is that the auto focus point array was (because Canon used the crop sensor 80D AF system without changing it to fit a full frame camera) jammed into the center of the frame... Here is the layout of the 6D2 in comparison to the layout of the 7D2...
This means that you most often cannot place a focus point on the eye of your subject when shooting a portrait with the 6D2. You are stuck with either focus and recompose or placing the eye lower in the frame and cropping. The first is sometimes difficult when shooting with a long focal length and wide f/stop and the second negates the advantage of full frame.
The 7D2 AF is better than the 6D2 because it has focus points closer to the edges of the frame...
My Sony A6500 has an AF array virtually throughout the frame which combined with Eye AF is great for portrait work. I can place the face virtually anywhere throughout the frame and can lock on with eye AF. Here are five examples of images, each with the head placed in different parts of the frame, one in the center and four in the corners of the frame. I was able to lock focus on each with Eye AF. These are all full frame and uncropped images.
I know that many photographers are going to say, "You don't need Eye AF because we have been shooting for years without it and have done just fine!" I'd counter by describing the capabilities of one of my first cameras...
It had no exposure meter - I either had to use a hand held meter or guestimate the exposure with the Rule of Sixteen...
It had no rangefinder or any other way to focus. I had to either measure the distance to my subject or guestimate it and then set that into the cameras focusing scale.
If asked; Do I absolutely need a camera with a built in meter or focusing capability, I could give the same answer as above "I don't need them because I had been shooting for years without them and have done just fine!"
BUT, would I purchase a camera for general use that didn't have a meter or some capability to focus... My answer would be a resounding "HECK NO! THIS IS THE 21ST CENTURY!" IMO, Eye AF is the 21st Century even though Canikon won't put it in their mirrorless offerings...
I modified the buttons on my A6500 to place Eye AF near the thumb of my shooting hand but, even better, the Sony 85mm f/1.8 lens has a focus hold button on the lens barrel which can be modified for Eye AF, This is great when shooting with the camera in the portrait or vertical position...