CAGR lets you compare investments held for different periods. Doubling your money in 5 years is a CAGR of about 14.9%. CAGR assumes a single investment at the start, so use XIRR when money was added over time.
Finance glossary
What is CAGR?
The compound annual growth rate: the steady yearly rate at which an investment would grow from its starting value to its ending value.