Ask HN: To what extend is multithreaded app server more performant?

I am in the process of having my first real life production app (Ruby on Rails). I have tried back and forth Puma and Phusion Passenger OSS.

I know the first one is mutithreaded and more performant, but Passenger is sooo easy to set up and config that I am already biased.

Is the different so important?

PD: The application is a kiosk-like remote managing for smart TVs