My Good Sam RM 7725 doesn't seem to follow truck routes and does route me directly, according to my settings, on the shortest route avoiding "small roads." It has not sent me on "truck routes" through cities. To me it's worth every penny to not come upon a low tunnel or bridge where I would have to stop disconnect the toad and try to do a u turn.
Since I am a solo rv'er, checking google earth constantly to see if there is anything ahead or using a smart phone is not an option for me. I do also use a map to look over the route before I set off for the day.