Any tote tank that will hold enough for even a small RV holding tank will be too heavy to move around. I have a 22 gallon Barker blue tote and it is the largest I would want to try to move. I even have put the large, inflatable wheels/tires on it to make it easier and quieter to move around. Yes, it gets towed to the dump by the truck BUT you have to move it from the trailer position to the truck. Sometimes, that is quite difficult and may be slightly uphill or in soft sand or grass. This is when the larger, heavier dump tanks can be too much. Personally, I would not get one larger than 25-30 gallons.
Ours gets used for both grey and black tank dumping. It is carried on the back of our trailer on the ladder and not in the living space of the RV. Besides that, both black and grey tank water smells horrible and I don't see much difference between them as far as cleaning out the tote. There is a hose connection for rinsing the tote and it works well.
Barney