My personal preference is Protect-All, which is great for painted RV and gel-coat finishes that are not oxidized. As close to wipe-on, wipe off as a cleaner/polish product can be. However, it's not a great choice for finishes that are badly weathered or really grimy.
Carnuba wax has an almost mystical appeal to consumers, so many polishes contain a few drops of carnuba so the label can claim it. However, a few drops of carnuba adds zero value to the performance of the product. Tom mentioned using it on gel coated fiberglass. Carnuba is a very hard paste wax that requires a lot of rubbing to apply and buff up, but it is probably the ultimate in weather protection and longevity. It resists sun and salt water better and longer than most any other product. It also produces a good shine if buffed really well.
Nearly all modern Car, RV, and boat polishes are synthetics rather than natural waxes. Most products are a compromise between three major goals:
#1. Clean and polish the surface to remove embedded dirt, stains, oxidation, etc.
#2. Leave a protective coating that sheds dirt and [maybe] reduces UV penetration
#3. Make the surface look pleasing (shiny)
If you have a fairly new RV in good condition, you need a little of #1, a lot of #2 and enough of #3 to please your senses. Some people like a "wet look" gloss, while others prefer a more stain finish. Whatever rows your boat...
If your RV has a lot of dirt or streaks on the finish, you need more cleaning action (#1). If the surface is oxidized you also need polishing. Polishing means grit in the formula and therefore more rubbing. It is essentially very fine sanding. Rubbing compounds are the extreme of that - a paste designed to gently remove a layer from the surface, all #1 and no #2 or #3 at all. Products labeled for use on "light oxidation" or claiming to "restore the finish" will have more grit (polishing action), but they usually end up sacrificing some of #2 and #3 to achieve it.
Paste waxes, of which carnuba is the extreme, are mostly #2 and #3 with only a little of #1. If the surface is very dirty or oxidized, you need to apply a cleaner or a polish before using the paste wax.