Jep, as I said it depends more on the roughness of the fabric than on the fabric itself. The coating is inside and doesn't make an real difference in the loudness, because the swish happens by rubbing fabric on fabric on the outside...
So my Polyamide ones (most of them) got fine fabric with more treads/inch, treadcount (estimated and compared to fabrics I bought by myself) 350-400. The polyester clothes are mostly more rough, mostly rain clothes and got compared also to fabrics I bought an treadcount of 200-300... These are my experiences from diy and I have already bought several meters of fabrics and also processed them into clothing...
But equal... To the question from the thread, I don't think you can wash or generally make them clothes louder, too... Softener, that's completely right, isn't good at all for those clothes especially for coated or stretch fabrics. However, for an uncoated fabric without stretch, it's not that bad either. More important is how alkaline the detergent is in general.