Should I Start an Enterprise Server Domain and Deploy My Application Into It, or Should I Use the glassfish_rails Gem?

To continue the question: I'm not sure what the second option does, or why I might choose one over the other.

Response: In a nutshell, a gem is an application runner. It can run your Rails application but nothing else. If you use the Enterprise Server v3 Prelude installation, start the domain and deploy. You can deploy several Rails applications (or Java EE applications even) concurrently with a different context root. This gives you access to different containers such as web and EJB and also to the Update Tool. Enterprise Server enables you to host not only multiple Rails applications, but also any other Java EE application.