User Experience design often is about human psychology. When designing forms which have users make a choice, keep in mind that different form designs may result in different user behaviour. Users are generally lazy: When there is a checkbox, people usually just leave it as it is (checked or unchecked). When using two radio buttons instead, people are forced to make a decision. Depending of what your goal is, choose the form design wisely.
Colleen Roller has the full article.
Extra tip: Do not only offer choices, but list consequences right away.