As a Java developer, I have to say that popularity [with clients] is not why I chose the environment (if it was, I'd still be using PHP), but because of the ecosystem of *useful* and *well written* libraries. From big frameworks like Spring MVC and Hibernate down to little utilities like OAuth clients and date handling utilities, just about anything you can need is there; just add a line to your maven config and it's downloaded and configured automatically. .NET is *almost* there these days, but doesn't have quite the slickness (NuGet lags a little in usability to maven, IMO) and there's a larger proportion of libraries that are buggy in my experience. But I'd suggest that anything *outside* of the CLR/JVM environment is taking a bit of a risk, because the farther you get away from these environments in which the majority of professional development is performed the more likely you are to find libraries and frameworks that are badly thought-out or are, frankly, badly-written.