title: jRuby on Rails vs Grails
body: <p>I'm looking to develop a greenfield web application which will reuse a lot of Java components.  To me, the obvious options for this are Grails or jRuby on Rails, but I'm having trouble finding objective comparisons of the two.  Are there any clear reasons to pick one over the other with respect to:</p>
  
  <ol start="5">
  <li>ease of integration with existing Java components (outside the persistent domain), e.g. JMS, EIP</li>
  <li>support for functional testing frameworks</li>
  <li>performance on a single machine</li>
  <li>scalability</li>
  </ol>
  
  <p>I am <em>not</em> looking for answers relating to the availability of developers or activity of communities.</p>
  
  <hr>
  
  <p>(I've checked <a href="https://stackoverflow.com/questions/2765512/grails-vs-rails">Grails vs. Rails</a>, and it's not relevant to me)</p>