Really nice article, I prefer multiple repo(s).

Recently at work we had to go from monolith to microservices architecture, we split and minor-refactor our codebase into several repositories, this allow to use-test-deploy each one independently or together as a framework, this last one is specially usefull when you want to test compatibility between versions.

Since each microservice could grow at its own pace, versioning is very important. Module A could require B as its latest version, but Module C could only use B at v0.15. This dependencies can by explicity specified in your dependency manager file, in our case composer.json.