There is extra stuff you are not considering, the eyesight of the user. What is smudgy to one person can be clarity to another. It all depends how well you personally can resolve the resolution on the screen and naturally gets easier the larger the display size. I do love high resolution small displays, as they have a paper-like quality due to the high DPI. However you still tend to have to zoom web sites a little even if they fit perfectly, for legibility.