1. As it is already mentioned, if metadata (data about timeseries) are already in PostgreSQL, then it is nice to stay in the same database engine for querying data with joins of both metadata and timeseries data, so there is no need to implement integration of the two source in the application layer.
2. Also related to the first item: advantage of already knowing PostgreSQL API. ClickHouse has different management API, so it is necessary to learn. While if you know PostgreSQL, you don't need to learn new management API and only timeseries specific API of TimescaleDB.
3. ClickHouse doesn't support to update and delete of existing data in the same way as relation databases.
Then the final decision still depends on your need.