the denser the pixels the greater the image quality.
the difference between 22" and 23" should not be terribly significant though.
if you have better vision then go for the 22" as you can definitely benefit from greater detail. if you have average or poor vision go for the 23" as you will not notice as much clarity loss and can benefit more by being able to see everything clearly.
there really is no right or wrong answer.
other factors affect image quality as well such as the type of lcd panel they use.