I believe all medical school line of credits are not locked. Assuming this, any bank should agree to the prime minus 0.25 that is currently offered by at least Scotiabank and RBC. If not, I would move. The savings depend on your outstanding debt but what's more important to me is a bank that will give me the best deal, especially considering their future business if they win my loyalty.
Remember to try your best to work with a representative who is well versed in professional student lines because not all are. Some banks have a list on their website that tells you their professional students reps in each city. I'm currently with Lynne owen at the downtown Toronto branch at queen street west and university avenue. She applied for the minus 0.25 without me even asking.