James, Symmons makes an excelent valve. We have sold them for years. In the long run I think the symmons holds up better than the others, But I prefer the delta monitor for style and features of the tempeture adjustment. You have to decide what’s more important to you. Good luck,
Symmons uses to thermal motor to control temperature, which is more accurate, but also, more expensive to repair. I always use the Delta Monitor 1500 series for its separate temperature and volume controls.