* I like the concurrency model better. Lightweight processes vs callbacks and futures. I find processes as concurrency units maps better to problems I had to solve. So there is less impedance mismatch. That makes a huge deal in a larger project. (eg.: a user request as an isolated process vs a chain of callbacks). OS design got this right years ago -- think how most modern popular operating systems represent concurrency - an isolated process.

* Safety & fault tolerance. Processes are isolated. So you can build very robust systems. That simply puts money in your pocket just due to ops costs. A non-critical / experimental part of backend is crashing at 4am and restarting? No, problem, keep sleeping. Rest of the service will stay up and you can fix it in the morning.

* Debuggability and inspection. BEAM VM comes with built in ability to debug, inspect and trace out of the box. That has saved so much time (and money) over the years.

* Hot code reload. This is a first class feature. We don't rely on it to do upgrades. But it proved invaluable to fix an issues or two for a high value customer without taking down the services. Or simply to add extra logging to monitor a pathological edge-case.