Hi Ian. A truck stop, for me, is a commercial gas station and restaurant/store where there is a large lot in back where the trucks spend their over-nights. A rest stop is a provincial (or state) run pull-off, sometimes with no services, sometimes with a rest-room. The thing is, commercial trucks are allowed to stop for 8 hours or more for their legally required off-duty time in a provincial rest stop, but RV's of any sort are only allowed to stop for 4 hours, and "camping" is not allowed. So, being a law abiding and quiet sort, I follow that rule. Lots of people don't, I guess, but I do. Plus, as I said, I find trucks stops safer.
I am either in a truck camper towing a car trailer, or in a bus conversion class A with no slides. If you do have slides, I would keep them in at a truck stop, they are used to parking in 10 foot wide spaces so a slide might get clipped. At provincial rest stops you are usually parking on the side of the roadway, so quite un-level and again you wouldn't want to stick a slide out into the active roadway. There are a couple of rest stops on AR 20 with large lots for parking, one on the east-bound side coming into Quebec City, and on on the west bound side coming out of Riviere du Loup, all the rest you have to park along the side of the road. In Ontario they have all those new rest stops with expensive gas and over-priced fast food outlets, and they usually have pretty nice parking for large trucks and rigs like ours, but I've never over-nighted in one. There is a nice place at exit 750 off the 401 near Morrisburg that I've stayed at, if you like diner food it's a classic.
Brian