I give my .02 worth.
The Tree Boss is made by Red Boss out of PA. It has been around for many years and is a great product if you handle lots of B&B it will save at least one person off the crew so it could be worth it for some. I've seen one good employee load/unload trailers with this. You definitely need a good operator. Someone that squeezes the ball too much will tend to misshape the ball especially if you handle it multiple times. Also if you are handling larger trees there is no rest for the top meaning that when the operator is driving and spinning around the trunk can wallow loose in the ball especially if the driver is rough and the rootball is wet. I had the opportunity to by one many years ago for 8K and wish that I had.
The Tree Rex is made by Dutchmaster Ind. out of Canada. Similar to tree boss and they make great quality equipment.
I own a set of Nursery Jaws made by Diversified Products in IA. It is possible to load and unload alone but most times a helper is needed to stand the plant material upright. There are several companies that make similar looking attachments. I have the 6' long jaws where I can reach completely across a trailer without bumping into the side of the trailer. I am also able to carry 3 30" rootballs in one grab and there is a padded bar for the top to rest on. Also since the angled forks are adjustable you are able to pickup more sizes of rootballs than the tree boss.