Hello Norman,
If you decide to go for a hitch drive insist on a demonstration at the place you want to use it. My reason for saying this is that if you research this forum you will find a considerable number of contributors who have bought a hitch monted mover, only to regret the purchase becuase it will not work safely on slopes and rough ground.
Points to consider:
Is it easy to fit,
and when it is not on the caravan is it easy to carry to and from the store.
Will it work on the ground over which you want it to move your caravan, dont forget that if the ground is wet or slippy (autumn leaf fall etc) it will have much less grip.
Does it clear all the features of the caravan (gas bottle locker and chassis structures etc)
Can you see where you are going when you operate the mover?
The general consensus is that the hitch mounted devices are only really suitable for hard flat, level ground. If you have slopes, gravel or rougher ground then the chasis mounted devices are generally more suitable.
A further point to consider is safety, Many of the hitch movers will claim they have enough torque to move big caravans, yes the wheel can turn with lots of power but can it grip the surface? That is totally dependant on the weght (Force) pushing it to the ground, and the friction between the wheel and the ground. The force is only going to be about 150Kgf (nose weight plus mover) and that is a small proportion of the total caravan mass. Just as important as being able to push or pull the van, is the ability of the mover to stop and hold a caravan on a slope. As a guide, if you feel you could not stop of hold the caravan in a given situation, then it unlikely that a hitch mover will be any better, and dont forget that in wet of slippy conditions, the mover has even less grip.
By sharp contrast, the chassis mounted devices have about half the weight of the caravan on each wheel, and this affords them much more grip. The larger diameter of the main wheels also means they can better cope with loose surfaces such as gravel. Most makes have a remote control box that allows you to stand to the side of the caravan so you can easily see when you are moving close close to obstructions.
Do you home work, ask each possible supplier for a demonstration.
best of luck and I hope you can continue to enjoy caravaning without the physical strain.