Chris Webb performs a test but gives us a warning first:
This is a post I’ve avoided writing for many years, and before I carry on let me make one thing clear:
Doing bulk extracts of data from a Power BI semantic model is a **really** bad idea
My colleague Matthew Roche wrote a great post on this topic a couple of years ago that is still relevant: using Power BI (or Analysis Services) as a data source for other systems, including other Power BI Import mode semantic models, is an anti-pattern. Power BI is optimised for small, analytical queries that return the amount of data that can be visualised on a single page. It is not optimised for queries that return millions of rows.
After the warning, Chris still gives a performance breakdown for extracting data from a semantic model in Excel, using automated MDX and DAX.