I love our Zodi Extreme and have used the other Zodi system, eccotemp L5, and simple heating a pan on the stove. Of those, the Zodi Extreme has been our favorite hands down. I have no experience with the road shower but I can't see getting 4 good, hot, pressurized showers out of one. We have lots of shade in the south so it may work better elsewhere.
-It's simple and requires no batteries or power of any kind.
-It gives a good consistent temperature shower which is something that I hated about other systems I tried. (no more hot, cold, steam, etc)
-It's very frugal on water so there isn't waste getting hot water back to the shower head each time.
-Since it's portable you can haul it down to the creek or lake to refill (I only use it for showers, not kitchen duties)
-I adapted a kitchen sprayer (bidet sprayer actually) to our hose for complete control of flow.
-You can warm the tank by the campfire to reduce stove use
-It could work in the house for times when the power is out.
-Travel with it full or empty depending on water sources
-It's not extra weight on the roof
-Heats up to shower temp quickly
-You can set your shower tent up away from the vehicle/tent/trailer/etc. to keep the runoff away from the common area
-We typically get 2 showers out of one fill (but have gotten as many as 3 before) Mom and Daughter go and then Dad and Son go
-I chose to not get one with the separate burner since we almost always have our stove setup.