Some smaller lenders like credit unions and other alternative lenders may be able to offer lower rates than the big banks like BMO. However, big banks and other A-lenders typically have more stringent lending criteria that allow them to offer lower rates than you can find elsewhere because they opt for less risky borrowers. Smaller lenders may be able to offer mortgages to people with unique employment situations or poor credit, but they may charge higher interest rates as a consequence.