If you have a motorhome and a toad you have a second means of transportation if one breaks. A 5th wheel rig and a motorhome will get about the same MPG but with a toad you save on gas when the motorhome is at a destination. If you're camped and the wife wants to go somewhere alone she'll be more comfortable in the toad (sorry if you think I'm being sexist, mine wouldn't drive the motorhome). The toad is much easier to hook up than the 5th wheel. If you have pets the motorhome is easier for them to travel in. The tow truck and the 5th wheel are much harder to get into than the motorhome and toad. Although the motorhome will be used for long mileage runs, the yearly mileage will be minor compared to a 5th wheel tow vehicle so the times between servicing will be quite long (i.e. $/year).
