This is a very difficult question to answer, although after reading digital camera tech’s answers, I would think twice about Sony and I would add reputation for good customer service to the list of how to choose a camera.
The only way for an individual to know the answer to most of these questions is to read reviews at several sites and ask friends. Many review sites have sample images that you can look at, including ISO tests. It’s a good thing that you know about purple fringing as this is the evil among lower price digital cameras.
Some random thoughts…
Lens quality – You’ll have to trust the reviews and start with the known brands. Nikon and Canon make good lenses. Schneider and Leitz are good lenses that are used on Kodak, Panasonic and Leica cameras.
Brand – The same names come up. Nikon, Canon, (even) Kodak, Olympus… I’d like to include Pentax, but it doesn’t seem their film expertise has transferred over to digital yet, as they are quite conservative.
CCD/CMOS – Most are made by Sony. CMOS is Canon’s. One thing that you CAN do is look for the sensor size. They are measured in a very arcane manner and their size is expressed in terms of inverse numbers. The larger the number on the bottom, the smaller the sensor. In point and shoot cameras, look for a 1/1.8 size as opposed to the more common 1/2.5. In general, a larger sensor will give better images.
Fringing and ISO noise – See reviews of the cameras that you are interested in after looking them over based on the first three items.