Hello Stephanie,
I have the full kit C3, the 50mm Cintar, the 35, the 100, the accessory viewer...
I also have a beautiful Zeiss Ikon Contina III, including the 70mm lens. And my collection includes the Retina IIIc that you mentioned. If I were to have to decide where to spend my hard earned cash, knowing what I know from experience from these three cameras, it would be a damn hard choice between the Zeiss and the Retina. The Argus is a very cool kit, but it loses out slightly in image quality and in 'usability' to the Contina and the Retina. And the Retina has the coupled rangefinder, so... that would be my "pick one for the desert island" choice.
Hold all three in your hands, and you will see what I mean, the engineering of the Kodak AG is definitely superior.