Here are two links that I found useful today:
Which developer do you think is going to be more productive? The dude having to know 3-4 different technologies, or the dude who just needs to know JS?
The developer that uses the right tool for the job will be more productive.
That means using a language with static type checking and a productive debug environment. Learning a new system infrastructure takes time, but only finding out about easily preventable failures during testing instead of compile time costs more.
Consider the postage stamp: its usefulness consists in the ability to stick to one thing till it gets there. -- Josh Billings