Our first year of full-timing was in a 35' fifth wheel, pulled by a one-ton, crew cab, dually diesel pickup. We switched to a motor home solely because the trailer was too heavy for the pickup and we didn't want to either downsize our living space (again) or move up to a medium duty truck.
That was seven years ago. Newer pickups seem to have more towing capacity than our old 1997 F-350 did, so if we faced the same problem today we might have simply bought a better truck.
That said, there are advantages to both trailers (especially fifth wheels) and to motor homes.
For the same amount of money, you can get a much nicer truck and fifth wheel than you can a motor home and toad.
A motor home and toad are much more expensive to license, maintain, and insure than a truck and trailer.
A trailer and a motor home of equal length will provide more living space in the trailer. The cockpit area of the motor home is essentially wasted living space. Yeah, you can turn the driver's and copilot's chairs around and make guest seating, but how may days of the year do you use that?
have deeper slideouts than motor homes, giving you more floor space. In a motor home, there needs to be room to move around inside while it's on the road, so slideout depth is limited.
Both fifth wheels and diesel motor homes are pretty immune to being pushed sideways by crosswinds and truck bow waves. Travel trailers and longer gas motor homes (with their relatively short wheelbase-to-length ratio) are more difficult to drive in those circumstances.
When traveling in a motorhome, rest stops and overnight stops are possible without leaving the comfort of your rig. (Unless the dog wants out.
Passengers other than the driver can more around, use the bathroom, etc. while on the road in a motor home.
I could hitch up our old fifth wheel in about the same time it takes to hitch up our toad, so there is no difference there.
Motor homes, especially diesel pushers, generally have more basement storage than trailers. OTOH, our fifth wheel had more inside
storage than our motor home does.
Once we are at our destination, it is a lot
more pleasant to go shopping, sightseeing, etc. in our toad than it was in that huge pickup. As a bonus, our toad is a Ford Explorer, which allows us to travel on roads that we couldn't with that big wide truck. It also gets better fuel economy.
In summary, I think a motor home, though more expensive, is a better way to go if you travel a lot. If you tend to park in one spot for long periods of time, the additional living space and inside storage of a fifth wheel is nice.