I've been using the Coava cone off and on for a few years and I like it. Lately I've moved back to paper for the most part, as I'm trying to learn "the right way" to do a V60. But this morning I did a metal cone actually.... and it didn't work out well. It was kind of an experiment to see what'd happen if I pre-sifted out the fines (I have a 500 micron sieve). Alas, this led to an extremely fast drawdown. I knew that fines slowed drawdown in paper, but people don't talk about metal out here very much, hence the experiment.
I'm not sure of the micron size of the Coava...