I am a Garmin fan so that would be my recommendation :) It depends on what you get used to. The Garmin has a lot of material that is useful for RVs. To the best of my knowledge the only lack is low clearance information. The reality is that most clearances that are less then 13'6" are clearly marked far enough in advance to take an alternate route.
The problem with Trucker/RV routing is that it takes the most direct and the least interesting route from point a to point b. From our standpoint that misses the whole point of traveling the roads of the US. Anyone can plot a route with maximum use of Interstates, the GPS just wakes you up to take the next exit. We avoid Interstates where ever possible so we want a GPS that caters to that desire. I know how to make the Garmin develop a route we will enjoy.
Features you may or may not want. Traffic, we don't have it because I can get the traffic info I need from Google Maps and from Waze on my phone. Points of interest (POI) Bread crumb - our current Garmin leaves a trail where we have been. Very nice as in the current locale the roads have been changed and the database has not been updated, the blue line shows me I am in the actual route I want even though Garmin database has no road there. Also when backroading with no real destination the track gives me a way to retrace my route.
