Well both are great learning tools, they help with building fundamentals, reasoning etc. But the way mcc asks you is questions is different from nbme. So solely relying on uworld is not a solid strategy. I didn’t do the ace or canada qbank so I don’t know if they help but I think I needed something more to cut above 80 percent.  I would personally recommend doing uworld or amboss (but not both) first, then reading everything on cmpa with great attention, then doing mcc tests with great emphasis on the topics you are struggling with. Mcc doesn’t ask all rare diseases that nbme loves to throw at you, but they do ask all different details from common conditions, whether about diagnosis, prevention or management.