I can bump your topic but since I have only done RAGBRAI in a motorhome I cannot make the direct comparison you seek. The MH/RV option is pretty painless. There are usually plenty of camping spaces (this year’s start town being a MAJOR exception, still mad about that….) and they are frequently convenient to showers and other amenities. If you want to run the generator and AC all night long, no one complains. Routes are good and access is good, with the occasional exception. The biggest downside to providing your own transportation support is that you need to find a driver. But you can take all the gear you want. If you have a few people sharing the cost of operating the RV for the week you will generally pay less than the cheapest charter prices I have seen. Unless you have to rent the RV and then I think a charter is cheaper, but the beds are better in an RV, there is AC if you need it, and overnight storms are no big deal.
An RV is a pretty nice way to do RAGBRAI but having studied them from afar I think that charters are too. If you stay in an RV you will have to work at it to make the connections with your fellow campers that seem to come quite naturally for those who do the charter or the Register baggage truck thing and tent camp. I’d like to try that some time. Like RAGBRAI itself it might be a one time thing to cross off your bucket list or it might be completely addicting. Depends on you.