All one-handed "dollies" and "hand trucks" are just passing fads and gimmicks for all except the lightest-duty applications. That's why the two-handed, wide-framed hand trucks have remained the standard for hundreds of years. There's nothing like being able to grasp your hand truck with two hands and maneuver it, push it, shove it, manage the stairs, and make it do what you want it to do. You simply can't do the same work on a single post handle that you can with two handles spread wide.
Also, not all pots are strong enough to be abused by a clamp or a wire or a bar that lifts the pot, or grasps at the lip. That amounts to either destructive abuse of a beautiful and expensive pot, or sometimes the complete annihilation of a cheaper pot. That's why our forefathers invented a flat platform for hand trucks hundreds of years ago.
If you want to start with the correct tool from the beginning, and not throw away your time and money, then go with either of the following two hand trucks from Nursery Enterprises for large potted plants. There's nothing like these two potted plant hand trucks—they have no competition!
I've used the bigger one for years. It's allowed me alone to do the work of a team of men--all without damaging my back or my expensive pots.
http://www.nurseryenterprises.com/15-gallon-tree-dolly.html
http://www.nurseryenterprises.com/large-pot-dolly.html