If you're going to do a 5-4 1/2" disc conversion, I'd buy 15" rim to go with it. You have many more tire options and lower prices than what you can get these days in a 14" tire.
I could see what your saying but im gonna try to reuse my 14 inch goodrich tires they only have about 500 miles if not less on them. If i dont see much on 14 inch then i guess ill go 15inch.