[user5994461]

Ansible has everything that's needed to automate instances, security groups, ELB, S3, RDS and few more things. I automated all the infra for a startup mainly with ansible (tens of services and a hundred hosts).

Terraform has better support for some static things, mostly VPC, routing tables, gateways. I've had infra retrofitted in terraform but honestly it's more for the show and as a documentation. Low level needs only be setup once and it's always been done manually forever ago.

If you were working around 2014-2017, both tools and many AWS services were new. There were significant gaps in support as well as a few bugs. Had to run from the beta build regularly. It is much better nowadays.