The main benefits touted are that Podman can run rootless containers and it doesn’t need a daemon compared to Docker. However those comparisons are less relevant now than they were a while ago because Docker can now run rootless containers and Podman has developed a heap of systemd hooks that effectively use that as the daemon. It does have some good features though, like being compatible with Kubernetes manifests.

If you’re happy with portainer and Docker I wouldn’t bother migrating.