Microservices are less efficient, but are still more scalable.
Servers can only get so big. If your monolith needs more resources than a single server can provide, then you can chop it up into microservices and each microservice can get its own beefy server. Then you can put a load balancer in front of a microservice and run it on N beefy servers.
But this only matters at Facebook scale. I think most devs would be shocked at how much a single beefy server running efficient code can do.
Servers can only get so big. If your monolith needs more resources than a single server can provide, then you can chop it up into microservices and each microservice can get its own beefy server. Then you can put a load balancer in front of a microservice and run it on N beefy servers.
But this only matters at Facebook scale. I think most devs would be shocked at how much a single beefy server running efficient code can do.