The benefits of polyglot persistence for microservices are:

Services remain loosely coupled.

Based on the specialized data store requirement of the service, you can choose the best, most reliable, and scalable data store with a relatively long history of use and a proven record of success in the market.

If multiple vendors or open source database engines are available to serve the chosen data model, you can make the database choice based on your team’s skillset or preference.

The benefits of multi-model persistence for microservices are:

You have a single multi-model database engine to manage instead of multiple kinds of databases.

You only need to learn one semantic model for interacting with the data stored in the database.

Managing one database engine type instead of several makes administration much easier.

There is only a single vendor license to manage.

https://medium.com/design-microservices-architecture-with-patterns/microservices-database-management-patterns-and-principles-9121e25619f1