We have overnighted(not camped) at Casino's, Rest stops, Box store parking lots, Truck stops, Camping World's, Mall parking lots. Do not have any real preference since convenience is the primary requirement. Have water, hot water, toilet, DC lights, heat and fans. Don't carry a generator so no air conditioning. Most if not all of our travel is in the Wstern States and in most cases cools off nicely in the evening. Walmart's cost too much to camp at(store purchases) but most have parking lot security. Always ask permission even if we see other overnighters. California Rest Stops are the least secure but have not had any issues to date. RV and personal security is provided by Smith and Wesson!
The way we look at it is we are self contained, why pay a RV resort or campground $30 to $45 just to sleep a few hours? When we really need a rest or longer stay, yes we pay to stay in a commercial campground. Different strokes for different folks.