I usually pick the file size that gives me the maximum amount of compression without loss of image quality.  So it's important to keep your eye on that little window.

"It is good to see ourselves as others see us. Try as we may, we are never
able to know ourselves fully as we are, especially the evil side of us.
This we can do only if we are not angry with our critics but will take in good
heart whatever they might have to say." - Ghandi