[dkersten]

If every other aspect of the applications (including the teams behind them) are identical, then the language/framework which is the most suited to developing new ideas and features is the one that will be most successful. For example, if you were using (to pick an extreme case) Lisp and COBOL, the Lisp version would have the advantage because new features could be implemented in a DSL suited specifically to the task, while the COBOL application would take a lot of work to extend.

In real life, of course, the differences aren't this large and are usually overshadowed by some other differences (eg, competence of the team, overall architecture of the application, marketing.. etc) and the language difference advantage may be negligible in comparison.