i recently moved most of my containers to docker-compose+portainer, and it works great. did i have to? no. but like everything else unraid, tinkering around is itself enough of a reason.
nonetheless, using docker-compose is more than just having a CLI. some other benefits:
you can configure multiple images holistically. instead of individually configuring telegraf, influxdb, grafana, you could do all 3 in a single YAML file. you can spin up/down the whole "stack" (as portainer calls it) together.
less restrictions. dockerMan only lets you configure a subset of available features.
it's standard. you can share your YAML file with others, and vice-versa with or without unraid. and since this comes from docker itself, it will be supported well into the future.
the only downside i've seen so far in this setup, is that obviously a lot of things assume you only configure docker containers with dockerMan. yesterday i got a warning from "fix common problems" that my templates for some containers were wrong -- well that's because i deleted them since they were no longer needed.
edit 1: another downside...if you restart the docker service (reboot, restart array, etc), all the containers will use the settings defined in dockerMan. this means volume mounts, environment variables, could be wrong/missing.
edit 2: if you use dockerMan to pull down new images and restart the container, it will use what's defined in the template and "detach" it from the compose configuration. if you try to apply the docker-compose.yml afterwards, it'll complain that one of the services already exist. you have to delete it from dockerMan, and then docker-compose can recreate it.