Only you can decide if the fitting of any kind of mover is worth it! You need to balance the benefits/drawbacks of each system against you own perceived or real needs. However can I raise some of the issues that you might consider before taking a decision?
Generic types - There are basically two types of movers currently available.
Those that fit to the front of the caravan A frame (ball hitch or jockey wheel), that have their own battery,
And those that fit to the caravan chassis and drive the caravans own main wheels.
Availability- The A frame types need to be fitted to the caravan each time you want to use it, and it must be removed for towing. So If you want the mover on-site you must make provision for carrying it and its battery in the car or caravan and in doing so consider if you would need to lift it in and out. The chassis types are fitted and stay with the caravan at all times.
2) Weight - The chassis types are heavier than the A frame types thus reduce a caravans payload capacity by a greater margin.
3) Effectiveness - Regardless of the type of mover in use it is a physical fact that the pulling or pushing force (Drawbar) is directly related to the weight (Down force) on the driven wheel. A frame types have only their own weight and the nose weight of the caravan, whilst the chassis type benefits of the weight of the whole caravan on its driving wheels. This simple fact has a major impact on the safe usage of the mover.
The amount of drawbar required is dependant on the surface conditions, so having a clear understanding of the land types it will be used on is essential and will affect the type of unit you choose. If your need is to be able to move a caravan over hard flat surfaces, then the A frame types will perform quite adequately. For rough or uneven ground the chassis type will be more effective
4) Safety- Consider a flat surface leading to a downward ramp. On the flat surface either type of mover will move the caravan with safety. But starting down the ramp the weight of the caravan will start to push the mover, and could cause it to skid and loose control. The A frame units are more prone to this problem than chassis units
5) Cost- In general, the A frame types area cheaper than the chassis types, but cost isn't everything, so it is vitally important that you consider the job you will be asking the system to perform.