Let's say that Developer Alex has a strong background in Perl and is familiar with the Catalyst framework. Developer Bob, meanwhile, has a strong background in Ruby and is familiar with the Rails framework.
Alex and Bob get together on a start-up. Of course, each will have very good arguments for their own specialty. Each will have a good case for MVC skills being transferable across languages. And, each will be able to validly claim greater productivity in his own field.
How do you decide which framework to go with? What factors should enter into the decision? Is there a way to integrate both skill sets without hammering productivity? Is there a way to avoid this becoming a zero-sum game?