I think basically one is pretty much... just ginger ale flavor, and the other has more citrus flavoring as well.

Or, there are just two different buttons/labels for Canada Dry, from different... marketing epochs.

I think the Canada Dry that I'm thinking of, thats just ginger ale, is like a bronze colored can, and the '+citrus' one is green ... ?

I think they're the same, just different pictures. There are other variants of Canada Dry, but they typically incorporate other colors to distinguish themselves.

I'm guessing this machine is in a high ginger ale demand area.

Source: am Canadian

first one says caffeine free