Depends on your budget. I have a 3 burner Spirit at home. Works great and it's 25 years old.
I've got a 2 burner Spirit at the cabin. It weighs a lot less and tucking it away for the winter is easier. It's not the grill that the 3 burner is.
The dial thermometers work for me. You have to either learn the thermometer and what it says or calibrate it with a thermometer you trust as far as temperature reading. I just set the heat to give me the temperature I want to cook on the dial. I don't know what the grill temp truly is when the thermometer reads 400, but it's a temp that I use most often. Give or take.
Dunno about digital thermometers, but I would just learn how to cook off what it says.
I've read mixed reviews on all apps. When they work, fine. If the connection drops, not so fine.