I've got a 2016 X and just rented a Y while I was on vacation out in LA for the Super Bowl. I think the big difference is that all four doors can be controlled, fully opened and closed with the fob. If phone key works well with self presenting front door for the driver, phone key might work for when it is JUST the driver using the X, but when you have passengers, the keyfob has always been pretty important in the role of opening and closing doors for me - and also makes riding in the X feel like they are getting chauffeured for passengers. I might just take my phone with me if I go run a quick errand, but when I take the whole fam with me, I think I might still bring the key fob.