Given that both Ruby on Rails (RoR) and Grails can run on the JVM (Java Virtual Machine), which language and framework enables equally competent and experienced developers to be more productive and roughly by what percentage? (i.e., deliver more business functionaity for the same amount of effort)
I know that Grails is easier for a Java developer to transition to. And I realize that the entire Java Library is available to a Grails developer. My question is regarding developer productivity in an environment where one runs on an JVM on Linux using the standard application servers (WAS, Weblogic, JBOSS, TOMCAT etc.). Note: JRuby will be used to enable RoR to run on the JVM.
I would requests answers from those that have done significant web applications development using both ROR and Grails.