It may work for others. But not in my situation.Isnt the use of both (smartphone & tablet) well combined on the 6Splus?
Take a look at my set up. In my situation there would be no way I could glance over while going 45mph down a city street with traffic and determine streets and landmarks while still maintaining control of my vehicle if I was using my iPhone - even though it's a 6s+ - which is why I use my iPad Air 2 in this situation.