Here's my take on the poly vs cotton debate. Back in the day (think polyester double knit of the 70's) the first polyester threads were so tough you couldn't break them with your hands without cutting yourself. I believe this is when the 'debate' started.
Nowadays polyester thread has come a long way. It is constructed to the finest detail and can be made to feel and behave the same as cotton.
This is why I believe there is no more need for the poly vs cotton debate.