On trips I wear the BV2. Love the warmth of it (don't wear a balaclava), the nice view through the shield, etc. I just don't like having to put it on and take it off, and getting the mouth covering thing just right. Once it's just right though, it's sweet. On sub-zero days, I wear a turtle fur neck warmer and stuff it up against the bottom. Keeps all the cold air out of my helmet completely.
On warmer days or shorter trips, I wear an open face gmax helmet (true open face with no chin guard) with a $20.00 snap-on dual lens flip shield with a klim balaclava. Nice and light-weight. Need some of a windshield on your sled though or the wind comes inside to your eyes too easily.