I find the concept of "Pareto optimal" a useful one here: <a href="http://en.wikipedia.org/wiki/Pareto_efficiency" rel="nofollow">http://en.wikipedia.org/wiki/Pareto_efficiency</a><p>This opens up a second front: In addition to "is it the best choice for this task", it allows you to discuss whether the language is actually Pareto optimal for this task. Even "the best language for the task" may be able to use some improvement.