Many differences, in fact.
The most obvious one is that one is a language and the other is a word in the language.
But the more important difference is that dead languages stop changing. They become, to metaphorize the discussion, a noun. Living languages change constantly: they’re verbs.
And verbs aren’t things you study or idolize or forbid. Verbs are what you do. Living languages are performed constantly by the folks that use them. The meanings of the words therein aren’t determined by a dictionary or by an etymologist or by any expert whatsoever (possibly excepting, of course, technical jargon–but even there I’d make the case that that’s not an exception, were that case not a hijack). The meanings of the words are determined dynamically and cooperatively in the interchange between speaker and audience.
And the meaning isn’t just denotation. The meaning of a word includes its phonemes, its cultural baggage, its allusions, the knowledge of both speaker and audience, and more. The more of these aspects of a word you can yoke to your purpose, the more powerful your speech will be.
An ideologue, of course, might be willing to elevate principle over communication. He might decide that a phrase like “double-plus ungood,” even though it doesn’t communicate meaning as well as “malign”, is the word he wants to use, merely to promote a political agenda. Similarly, he might decide that the word “niggardly,” even though it’s going to distract and undermine his meaning more than a word like “miserly,” is the word he wants to use, merely to promote a political agenda.
But a powerful communicator won’t do so. A powerful communicator chooses the word that conveys meaning most clearly, without distractions, to the intended audience.
We each gotta choose whether we’re the ideologue or the communicator.