I considered most of the choices everyone put up here: Ruby on Rails, Groovy on Grails, Python/Django and then the Spring MVC framework in Java. I eventually picked Ruby on Rails.
Why? First, I needed the ability to develop features rapidly and with flexibility. That doesn't speak in Java's favor. Second, I needed to develop a website not a back office application. So the UI didn't need to be super sophisticated. A simple CRUD application that wraps the database and paints it on the browser was good enough. That decisively ruled out Java.
So I'm left with a dynamic language framework. I tried out Groovy. Since I didn't need interoperability with Java, that ruled out a plus in its favor (yes, I know JRuby is interoperable but Groovy still has '{}'). After prototyping something in Groovy, I noticed that the stack traces were not always enlightening for debugging, and the performance was slow compared to my Rails prototype. That eliminated Groovy.
Thought about using Python/Django, but I noticed that it would be more difficult to bring others on board, since the sheer volume of books in RoR >> Python/Django. Perhaps I could have given Python/Django further consideration, but it was time to make a decision, and I choose RoR.
