If your end goal is Sugarbush and Killington (and Burlington) you're better off (by like 10 fold) to end up in Waterbury/Waitsfield.

Northfield is fine. I grew up there for a bit. But it's not on the way to any of those places. If you want interstate you gotta go up the mountain. It's close to Sugarbush as the crow flies but in practice? That's not an easy trip. It's an hour (in GOOD weather, which it won't be if you're skiing/boarding) to Killington.