score:4
I don't think taking I-87 is going to be a serious consideration for a trip between Montreal and Boston. It's on the wrong side of Lake Champlain, so you'll have to go far out of your way and extend your trip by an hour or more.
The route taken by Greyhound is essentially identical to the first option given by Google Maps for a trip between Montreal and Boston. This route follows Autoroute 35 then QC-133 to the US border, then I-89 through Vermont to Concord, New Hampshire, then I-93 to Boston.
The first alternate route follows Autoroute 10 east, almost all the way to Sherbrooke, exiting at Autoroute 55 south to the US border, then to I-91 through Vermont to I-93 and following I-93 through New Hampshire all the way to Boston. This route passes through the White Mountains and if you are interested in seeing that, then you may want to take this route anyway.
The 511 thing is not unique to Quebec; every US state and Canadian province has such a system. You can check the Vermont 511 and New Hampshire 511 web sites for updated information about driving conditions along each route. At the moment your biggest concern will be the occasional bit of road construction. There seems to be much more of it in Vermont right now, but that may change by the time you take your trip.
Finally, since I live here, I can say that we are very good at keeping the roads clear. Even after last week's blizzard which dumped 60-90cm of snow, all the major highways, and most of the streets, were usable by the next day. Just try not to drive in a snowstorm and you should be fine to take either route. You'd be better served by checking weather reports and moving your trip forward or back by a day or so if necessary and if you can do so.
If you do find yourself driving on snow covered roads, keep your speed down, and watch out for idiots in SUVs whose vehicles are better than their driving abilities. I usually won't exceed 60km/h on a snow covered interstate highway, and I have seen plenty of people going faster than that wind up in the ditch - and one of them almost ran me off the road once. That was a fun morning.
Upvote:1
Within the United States, your "Route 87", "Route 89", and "Route 91" (typically referred to as "Interstate 87", "Interstate 89", and "Interstate 91") are all Interstate Highways, the top class of long-distance road in the United States. Consequently, all three of them will be kept as clear of snow as possible. Which one of them will be the best will be determined mainly by the weather on the day of your travel: a storm affecting one of them may miss the others.
I'm not as familiar with the Canadian side of things, but Google Maps shows the Canadian portions of the I-87 (A-15) and I-91 (A-10/A-55) routes to be similar grades of road, while I-89 quickly becomes an undivided two-lane road.