I should also have added - SQL on RDS, the license cost is baked in. You have to re-purchase the license every year. You don't have to do that with enterprise

I should also have added - SQL on RDS, the license cost is baked in. You have to re-purchase the license every year. You don't have to do that with enterprise licensing, which is a one-time upfront cost. You also can't overprovision, and you can't use alternate licensing models like MSDN.