I haven't used either at ATL, but, knowing the general layout of the rental car center, I'd say no real advantage. You can wheel the cart pretty much anywhere in the building.

When you return the car, if you pull all the way to the front of the line, you will probably have to walk all the way back to the other side of the building near the escalators /elevators to get a cart, so give yourself a few extra minutes. Like I said, it's totally doable, it's just not a super fast procedure.