Instead of getting a Macbook Pro 13" or 15", I was thinking of getting the Macbook Air 13" or 11", but checking the machines at Apple store, it turns out the density of pixels of the screen of the Macbook Air 11" or 13" is larger, so the font appears more "dense", and therefore smaller.
It turns out that the Macbook Pro 13" has smaller pixel density, and the 15" model has even smaller density, so they can have larger fonts, without needing to squint the eyes. The 17" model also has high font density as well.
If I want to get the Macbook Air 13", is there a way under Lion to make all the fonts larger (the webpage, the menu bar, all apps), without changing the resolution of the machine to something not the native resolution? (Native resolution is optimal on each machine.)