I agree with Berettaman on the differences between the two - as I understand it. It seems the Polartec product is more of an active insulation that is very breathable. As to the pure insulating qualities, I can't find anything on the Polartec Alpha with respect to measured insulating value ("R" value). I'd suspect its in the same ballpark as the better Primaloft products.

Adversity doesn't build character, it reveals it.