What are the benefits of a global reserve currency?

Let’s say we have two countries, country X and country Y. Country X has its own currency that is stable but stays within that country or at least has very little mobility. Country Y’s currency is the global reserve currency, which is also stable. What benefits does country Y have over country X.

All I know so far about the benefits is that you can control the economy better and can take out loans from other countries more effectively and other geopolitical benefits as well.