Rusty, while that is true to a large degree the flip side is actual combination and the way it acts in the car driving. Adding a bigger valve is almost always good but it can also backfire with slower moving air equaling a slower moving car.
Where the break point is I do not know. It's combo dependent. Get the combo right in one car it could still be wrong for another car with otherwise equally equipped gear. (Weight)
Since a smaller valve generally speaking adds velocity, it could be in the best intrest of a particular build to retain a smaller valve. If a larger valve always adds power and make the car go faster, then a 2.08 or 2.15 valve would be in all the heads.
