Performance is going to vary based on many factors. While I don't know that any file formats are better than any others, I would try making a performance recording:
I realize this reply may come a little late but I wanted to share some insights on our recent switch from Excel to SAS data sources.
After replacing Excel with SAS data source files, we did notice a slight improvement in the time it took to refresh data in a Tableau workbook.
However, there were other reasons why upgrading from Excel to SAS was beneficial:
- No need to worry about the row limit for large data sets (I believe the current limit in Excel is 1,048,756 rows)
- Since we do all of our data processing in SAS, we don't need to include the extra step of exporting the data as an Excel file
- Most importantly, Tableau will be phasing out legacy connections to Excel in 2019 (https://community.tableau.com/docs/DOC-22075)
If you are creating a new connection to a data source, then between the two options you are considering SAS is the way to go.
If you are going to switch from an existing Excel connection to SAS, then as long as the content and layout of your data source files are identical you should be ok. The only things you need to watch out for are that your aliases and formats will be cleared.
It was a bit of a pain to switch the data sources in all of our Tableau workbooks but ultimately better to have done it sooner rather than later.
Hope this helps.