A second Chawly Changer will double your coin capacity. This dispenser will always be able to give the change for a purchase, or accept the change from a purchase, unless you are given excess coins of one kind to make up for the lack of the right coin, or you are given a half-dollar coin. That doesn't happen very often. Most people don't want to carry a lot of change. More coins means more weight.
More capacity means a bulkier dispenser.
More coins are harder to count. Even when you have more coins, the dispenser will still be valuable to get you through the check-out line quickly , and to get rid of those excess coins. Dispensers ordered without keychains have no keychain mounting holes.