I think more flexible is a better word -- it can do more than what you can do when you bake a static image because you also use it to dynamically manage a running system post-boot.

Ansible can deploy all of your dependencies, keep them updated, push out configuration changes, and deploy your main application code.

I don't use AutoScaling, but no reason it couldn't be used with Ansible. The docs have a bit of detail on how to do it. http://docs.ansible.com/guide_aws.html