A big advantage of using the AWS SDK - if installed - is that no credentials need to be recorded in the environment variables when the application is installed on AWS infrastructure, and a so-called Instance Profile is setup for the EC2 infrastructure being used.

The AWS SDK can work with credentials, but default to the Instance Profile to determine the available permissions, as set in the IAM configuration of your AWS account. When your application is heavily dependent on AWS services, all permissions are maintained in the Instance Profile instead of using a multitude of AWS keys & secrets.

A proposal is to use http://ses or smtp://ses whenever you don't wish to use AWS keys & secrets.