To me it all depends on other factors. If you're programming in a Windows environment then I'd pick ASP.NET MVC using C#. I've worked with it before and while I

To me it all depends on other factors. If you're programming in a Windows environment then I'd pick ASP.NET MVC using C#. I've worked with it before and while I'm a Mac/Linux guy by trade, I found C# to largely be a pleasant language to work with. If you're on a more traditional Linux stack, I find Ruby has the best ecosystem around web application development. Its not the best for everything (for instance Python tends to have better libraries for more advanced math and statistics work), but I think Ruby is the best for rapidly prototyping and building out a web application. The packaging system, ecosystem, and huge number of available libraries are killer features, and you can always switch to JRuby if concurrency becomes an issue. If you build your application in the right way you can extract services and port them to Java or something more performant as needed if you hit the limits of a scripting language performance wise. This gives you a clear path forward as you need to grow and scale. Though a well constructed Ruby/Python/whatever app can scale fine if built well.