Top marks for Chidiock Tichborne's prison lament, with its "And now I live, and now my life is done." Not a polysyllable in the lot. And low marks, I'm afraid, for Samuel Johnson's "Rambler" essays.
And what about Master W. S., who knew exactly what he was doing when he took those doublets from Norman Law French, and ran away with the idea of glossing one by the other: "the expectancy and rose of the fair state" (Hamlet) or "exsufflicate and blown" (Othello) or, sometimes doing it not through those doublets but with lines following lines, and amidst Tichbornesque monosyllables, a line of Johnsonian Latinate polysyllables:
"No, this my hand will rather/The multitudinous seas incarnadine/Making the green one red." (Macbeth).
No rules of thumb, no guides by the pricking of my thumbs to tell that something wicked this way comes. It all depends on how you use them. either those once-inkhorn terms, or those honest kersey yeas and nays. Some people can handle, for example, both "polypragmonic" and "holmgang" at the same time. And some can not.
I can handle both.
It depends what you're writing about too. It would be difficult to write about human anatomy using only Anglo-Saxon words. Perhaps.
Juxtaposition can be fun. I once heard a British politician described as a "vainglorious twat".
Unfortunately I can't name the politician - we have nasty libel laws in this country. Nor can I narrow it down - he's not the only vainglorious twat in the Labour party.