They are very similar. Databricks SQL uses compute that has photon enabled. A traditional cluster with photon enabled does allow for a few more configurations to be set around the cluster architecture and settings. The traditional cluster will also have more libraries installed as it needs to run things in various languages, where the endpoints only needs SQL APIs.

https://docs.databricks.com/runtime/photon.html#limitations. This lists some limitations, although additional data source reads is in preview now.