The RX is the best value of the bunch. The RTSIII is a more solid camera, with the weight to prove it, best viewfinder, but much more expense and from a practical point of view, not much more functional. In fact, it is less functional with flash. You need to set the f-stop yourself. The Aria was my first Contax and the one I expected to love, but I didn't. What it does have is the matrix metering and great communication with the Contax flash. What it lacks is solid, sturdy build. It also is overwhelmed by anything other than a really small lens. Of course, mine tanked within two rolls of film, so not happy about that and the rubberized finish pealed..not so happy about that, but many swear by this camera. Wonderful size for lugging around with a small lens mounted...ie the 45mm.. I purchased the SLR for an alternative to my rangefinders. I use them for macro.. 100mm Makro is the best of best lenses and tack sharp for anything that a 100mm can do. Actually, found one NIB. The 100-300mm lens is really sharp.. but big. The 50mm f/1.4 is one everyone's best lens list, but I shoot mostly rangefinder in this focal length and wider. What I wanted with the Aria and the RX was the ability to shoot Velvia with a polarizer. So, as others have said, ask yourself why and what you are doing.
