Greater fuel bulk. This should only be a problem in wilderness or backpacking situations where most professional outdoor people do use the gasoline models. Higher cost per hour.
Propane is more expensive to run per hour.
However, if you camp only a few times a year, the overall convenience should overshadow the small extra cost. Then, too, if you hook up a bulk propane system, the running cost becomes considerably less than with gasoline. In fact, I it becomes extremely economical. Poorer fuel availability in rural areas. You will find it easier to buy a gallon of Coleman Fuel than a two-pound canister of propane in most rural areas.