To my knowledge there are three "RV" model GPS units out there.
The oldest is the Rand unit (sold under both Rand and Good Sam, but it's the same unit). The early production Rand unit's had some serious crash/freeze/brick failures. I don't know if the newer model numbers have fixed these issues.
It comes loaded with the the GoodSam/Woodhals RV campground directory.
There is the Garmin unit mentioned, this also comes loaded with a campground directory.
Then there is the Tomtom model. This comes with a discount to KOA (which would be needed).
On a feature to feature compare, I think the Tomtom comes up short of both the Rand and Garmin units.
Personally I prefer Garmin (I had the -original- Streetpilot, the Streetpilot i2 and now a Nuvi).
That being said -every- GPS will sometimes route you oddly, and once in awhile, dangerously so.
