We're using the docker executor type for many of our Circle Enterprise builds:
We love the faster start up time, but the consequence has been more flaky builds because we can't describe dependencies between the dockers as we can with docker-compose.
The difference between the machine and docker executors is 8x build times. On average our build times went from 8min to 1min. This is great when they actually run, but the flakiness makes it practically unusable.
Building new docker containers with waitforit or something similar installed is not an option for us.