A one-time download creates a file for the selected year range and content types. It is useful for imports, archive snapshots and tools where you want full control over when data changes. Use the federal-state feed for personal calendars; business snapshots stay in data export.
A calendar subscription keeps a stable feed URL in the calendar app. It is better for personal calendars because future years and source-data updates can appear without downloading a new file manually. Choose a federal state before adding state holidays or school breaks to the feed.
Business exports remain separate: use the data export when CSV profiles, delimiters, language or HR-oriented import formats matter. Use the federal-state feed for personal calendars; business snapshots stay in data export.