In reply to wi11:
I used old style Vipers a lot, including in Antarctica, but now have new Cobras, which have not been to Antarctica. The Cobras feel like they will be less-cold than the Vipers, but I never really got cold hands anyway, so it's relative. I did once try wrapping the upper shaft with soft rubber pipe insulation tube, available at most big hardware stores. Was definitely warmer but a little too bulky. I later put sheets of sticky-backed sandpaper-like material there, which improved grip with soft gloves and meant my hands were not directly on metal.
I agree it's mainly when daggering - I doubt actual swinging from the handgrip will make a lot of difference. As for swing and stick, I really liked my Vipers, and I don't think the Cobras swing and stick any better in hard water ice, though there is some noticeable difference with vibration dampening etc, but no big deal. The Cobras feel *lighter* to swing than my old Vipers, but that doesn't necessarily mean I like them more.