Generally speaking either interstate will be kept decently winter maintained, though of course on any given day the weather could be nasty and the going slow. Keeping the major interstates open is a priority for the highway departments.
I also think a car and motels or the train would be a much better plan than slogging it through with an RV, as well, all things considered. A lot of campgrounds are closed. I think there are maybe three campgrounds in the state of Vermont that are open during the winter.
You may also want to give some thought to chain requirements for the western mountain passes (the specifics of which I suspect you are already better aware of than I am). Chains or snow tires are not generally specifically required in the east, but appropriate equipment is, of course, a very wise idea.