Tbh Im not sure how much use the vehicle size facility is. Its rare indeed on a journey that you will find your caravan too high and roads with weight and width limit are usually clearly marked. The entrances and access lanes to some campsites are often very narrow but are always passable with care.
With this in mind my wifes car has the Garmin unit fitted with free live updates, speed cam database and also importantly a dashcam built in which is excellent. Throw in hands free and voice command and it all adds up to a highly efficient unit. It also warns of traffic issues and dangerous situations like severe bends.