Marco Russo and Alberto Ferrari take a look back at calculation groups:
The introduction of user-defined functions (UDFs) in DAX changes the way we think about code reuse. Before UDFs existed, calculation groups were the only mechanism for sharing common logic across multiple calculations. Many developers adopted calculation groups not because they were the ideal tool for code reuse, but because there was no alternative.
Now that user-defined functions are available, it is time to revisit this practice. User-defined functions and calculation groups serve fundamentally different purposes. Understanding the distinction between the two is essential for building well-organized, efficient semantic models.
Click through for a dive into these two concepts and when to use each.