I've had good luck with my Nuvi 50LM. Even with the camper overhand, in deep woods down in the valley it usually tracks very well. Only problem it has is keeping track of the elevation which isn't that critical. Comical though being at -2000 ft below sea level when on top of a 5000 ft mountain.
The LM stands for lifetime maps. As long as you upgrade it at least every 2 years and they support the product you can update for free.
Then you can add the POI files (this can be done to most GPS units). I have 4 files which list just about every government campground in the United States. This cover city, county, state, and federal. I've checked it against some small NF backwood 10 site campground which most list miss. Very easy to add.