Dalton is a better option than Mayfield. Doesn't make sense to downgrade at the QB position. If you're making a change, get an overall better QB (Carr) or a younger, more dynamic QB (Fields). But going from a better QB to Mayfield doesn't make any sense at all.
Eh, right now, Mayfield is better than Dalton. Not by much, but, he's younger, more mobile and better overall talent. That said, Carr is miles better than either one of them.