I have the Stanley Panel Carry, previously reviewed on Cool Tools, but greatly prefer the Gorilla Gripper, which works with panel widths from 3/8 to 1 1/8 inch. It is about six times more expensive, but it works significantly better for moving large panels.
The Stanley tool goes under the bottom edge of the sheet. This can be awkward if it’s heavy material, such as plywood, and seems more likely to result in damaged corners. Using the Stanley holder, I had to bend my back at an awkward angle to pick up the sheet — the length from the tray (where the bottom edge of the sheet rests) to the handle is too short. The Gorilla Gripper lifts from the top of the panel, so there’s less need to bend before lifting, and I can keep my back straight. Also, with the Gorilla Gripper it’s easier to adjust your balance, since you don’t have the friction of the material moving the tool from side to side.