I've used the following with heavy furniture and these straps were great. The person on the other end was my sister who is not big and strong, and she was very impressed how it made carrying the item easy.
You are able to free your hands for balance and/or guidance on hand rails, and they reduced fatigue while carrying. The weight was balanced and was felt more from the hips, not the shoulders. These straps are padded at the shoulders, but have a belt strap around the waist, where two buckles connect to two straps on each side of your waist that support the heavy object. There is a pad on the center of the back which adds comfort. The two straps provide balance to the object.
I have never used them on pinball machines, but they should work as an alternative for difficult stairs.
I have seen other cheaper ones (shoulder dolly), and have read complaints that the force is all on your shoulders, which can make it more difficult to stand or walk. And they also have only one strap which would make balancing tougher. Cheaper ones have no padding, and no waist strap, causing more force and tugging at your shoulders, which would cause more fatigue. These below are cheaper, and inferior.
I spent the extra on the grip system at top, and was impressed. I would like to try them with pins on stairs, but haven't had the need.