I had a friend that the family owned a Cadillac repair shop in the 60s to 80s, I used to hang out there a lot. They had one of balancers that did wheels on the car, but they were the only in town using one. I didn't see any advantage to it other than you didn't need to pull the wheel off of the vehicle. Unless maybe that you consider it's balancing everything that's spinning like the drum and rear axle. But axles are a perfectly straight part and brake drums have balancing weights on them when they were made so there is no reason they would be out of balance. When I to work at the phone company garage, we had a Coats tire machine and a Snap-On wheel balancer. I would take the wheels I had balanced and for fun I would stick a 1/4-ounce weight on the rim and spin it again and it would ask for a 1/4-ounce weight directly opposite of it. The balancer knows which sides of the tire needs the weight but you could also set it so it would only ask for weights on the back of the wheel in case you didn't want to see them. How much better could you ask for. I bought a used Coats tire machine and a Snap-on balancer to mount tires at home. Hardly ever use it, but they are nice tools to have. Years ago, had taken a set of wheels that I had sand blasted, primed and painted with quality automotive paint to have the tires put on. They scratched them up so bad that nobody but me will be mounting my tires ever again.