I would be pretty confident that each mover manufacture should have done enough research and testing to verify the chair or gears they use will be adequate for the designed loads. So provide teh weight and size of the caravan is within the manufacturers specifications either should work effectively.
Where there is more likely to be uncertainty is with the control systems the manufacture uses for the motors and the mechanisms used to apply the mover's drive roller's to the road tyres.
But there you may need to consider the reason why one design can use a gearbox, and the other needs a chain drive. This is most likely down to the placement of motor, and how well protected it may be from road dirt and kerbs. Another possible reason for the difference is the available space around the wheels and the movement caused by the swinging arm suspension units and or dampers (if fitted) chassis members
I suspect its more about which will fit your particular chassis arrangements best.