I do not see any greater "problem" with the radial zippers than with longitudinal zippers, why would there be?
As to insulative performance, a given thickness of dry insulation over a heat-radiating source, as in the radiation due to metabolic reactions in the human body, will result in a greater retention of said heat; this is why so many mountaineers will carefully drape their down jackets over the torso area of their bags and it DOES work, although there are more efficient methods as I suspect the Regulator system will prove to be.
The issue of a "draught collar" is an interesting one and my experience is that a fitted draught collar makes a given bag warmer by a considerable margin, which is WHY most reputable makers install them in their bags, especially the winter and expedition models. They DO NOT restrict circulation, the primary means of energy flow through your body and THIS, not some daft idea of keeping all the "hot air"inside your bag is what is crucial in retaining warmth.
My take on this whole affair is that some simply cannot refrain from making nasty comments and claiming the greatest knowledge of gear EVER, even when they do not/have not used the products they sneer at. I prefer to avoid persons of this type and the gear they make/endorse as they are not worth the effort/time to respond to their typical slurs, i.e., ...puny chest... Anyone with any real knowledge debates on merits, not by slurring people he has never met, especially by lies such as this.
Based on USE of Kifaru products and of that other brand, would I buy Kifaru again, YES, and I already posted on the other brand. 'Nuff said, thanks to all who tried to assist me with some REAL opinions.
