In order to understand the differences between KMS and MAK, you should first know what they mean. These were released by Windows when the Vista was released. MAK stands for Multiple Activation Key. Take note that the MAK can be used for different device activations. The MAK key can be typed in when you are doing the Windows setup.
KMS is known as Key Management Services. This would need to be used when you are working on trying to configure your server within the corporate network that you may have. KMS will also expire after 180 days. Take note that KMS is considered to be more appropriate for the corporate network.