As a caravan owner/user I have several friends with motorhomes, and when we toured New Zealand we hired one so a few points worth considering, perhaps...
1. Cost - much higher costs as you are buying a truck that has been modified by sticking the accomodation on the back. It WILL require taxing, motor insurance as well as habitation insurance, servicing costs can be high as many independent garages don't have the facilities to get a truck that high onto lifts.
2. Ease of use - many motorhomes are quite a bit smaller internally than a caravan, so can feel cramped. If you have friends in there is usually very limited space for seating more than a total of 4.
3. Mobility - there are two sides to this... a) If you tend to stay in one place for a while and use it as a base to visit other places (hub and spoke sort of idea) then it can be very inconvenient to have to pack up everything to go out for the day, and many supermarket car parks have very limiting height rules - this can be overcome by taking a small car with you .. but that is yet a further cost, and not a small one !! b) If you continually move from place to place (as we did when touring New Zealand) then a motorhome is ideal as the setting up/ preparing to move times are much smaller than preparing a 'van to move
4. Facilities - due to the limitation on size many motorhomes have small dual-purpose showers/toilets, smaller hobs/ovens and very little worktop space. If you buy one with an "over cab" space think about the ease of actually getting up there to use it !! IME the "ladders" are extremely flimsy and not easy to use !
There are those that swear by motorhomes, and those that wouldn't touch one, I think they both have a place, dpending on the lifestyle you want. I wouldn't swap my van/towcar for the type of holidays we have in UK/Europe, but there is no way I would use such an arrangement to tour New Zealand/Australia, that would be a motorhome everytime.
HTH, just my thoughts, nowt else