Cowboy vs. Pow

Cowboy aims to provide a complete HTTP stack in a small code base. It is optimized for low latency and low memory usage, in part because it uses binary strings. Cowboy provides routing capabilities, selectively dispatching requests to handlers written in Erlang.

Pow is a zero-configuration Rack server for Mac OS X. It makes developing Rails and Rack applications as frictionless as possible. You can install it in ten seconds and have your first app up and running in under a minute. No mucking around with /etc/hosts, no compiling Apache modules, no editing configuration files or installing preference panes. And running multiple apps with multiple versions of Ruby is trivial.