I don't know about you, but in the winter my top two criteria for snowshoe hikes are proximity and access. During the winter, I rarely even see tracks after 1/4 mile down the trail. So, almost anywhere close by with a good parking lot will do for me.
All the options you mention should be fine. If you do want to go to VT, I wouldn't bother going to Killington. I'd think that Route 9 to the Glastonbury area would be better. You could go up the firetower and get a good view of the Somerset Reservoir. Another nice route might be south from Manchester to Stratton Pond.
Of course, during the winter I'm never too concerned with mileage or getting to the top of anything. I just like taking a nice walk in the woods with a few friends and my dog.