Before using Terraform I tried to use Puppet to manage AWS infrastructure. It was a fun but short adventure. The idea of having all your configuration in one tool is nice but Puppet just isn't that tool. The one thing I found lacking the most, which made Terraform the tool for the job, is awareness of state. Having the triangle of what configuration you want (HCL), what configuration you expect to have (state) and what configuration you actually got (real world), with the tools to observe the differences between these and the ability to make careful changes is just what you need for important infrastructure changes. With Puppet every change felt like Fire-and-pray. Sure you can run a 'noop', but if anything changes in between that and the actual run that could trigger another resource you would be catch by surprise. On OS/App level the impact can often be contained, but on infra, not so much as you would have reduce the powerful features of Puppet to much as to it not being a benefit anymore.