I would go with your Undergrad school waiving your tuition. I am in the exact same boat as you with a different program (Master of Social Work). I am choosing to go with the school that will allow me to graduate debt free with a similar education as the other school. I have had debts linger for awhile and do not want to experience that again. If you are comfortable in your surroundings and are familiar with faculty, you may not get the same experience at the new school. As much as I also want to try a new school out, and the new school carries more prestige, at the end of the day, I want to get ahead with finances rather than have to worry about how to pay off debts upon graduation. Good luck!!!