I've witnessed numerous discussions in which a photographer has proposed the idea that there is one perfect size for every image. Making that image smaller or larger somehow diminishes it. I don't bring this topic up to attack or defend it, but rather to ask the simple question how do they know? In order to determine that there's one perfect size for a given image we would need to make it in every possible size to determine which one is the best! I don't ever recall anyone actually doing this. Perhaps the best size is the one you make.