Having done it both ways, anecdotally speaking, I prefer to not disturb a single root hair on a root ball during transplant. I take the whole ball and plop it into its new home. dirt and all. While it does then seem to take a while to get established as, I guess, the roots have to find their way out of the ball, I'm of the opinion that disturbing the root ball causes subtler long-term damage to the plant that doesn't show up much later but isn't trivial.
