I like the thumbwheel and have no desire to run my train with my phone.
I call it an 'index finger wheel'. My arthritis is already so bad in my thumbs that I have gotten pretty good operating it with my finger. I bought a WIU as soona s they were on the market, and tried the phone app for quite a while. I think it is really slick, but I had trouble using it. The physical buttons on the remote work better for me. Now I should get a second remote.
Again, this is all my opinion of personal preference. The WIU and app are the way of the future, and there are many advantages for the average modeler. There I said it, I'm Abby-Normal!