I can't help you much but I would not chose a tower on this criteria alone. I have had several computers and I have never had a power switch go bad.
I would concentrate on a tower with plenty of room and decent air flow. And, at least in most cases, I would avoid the towers with power supplies included. Or at least buy a separate (good quality) power supply. That is what I did and it left me with a power supply that I could use to diagnose problems with. Most power supplies that come with computer towers are of poor quality.
I am not sure why you have been having problems with power buttons but I think it is a fluke.