The key questions to consider are: Do you pay your parents anything toward the household expenses they provide (room and board)?
Do you pay the college tuition all yourself?
Add it all up. Do you pay more than 50% of all expenses incurred for your "support"?
Viewing it as a "family unit", your exemtion gets a bigger bang for the buck on their return rather than on yours. (Their marginal bracket is likely higher than yours). Most kids in college f/t stay on parents' returns until they graduate or reach age 24.