The Z750 has digital anti-shake. It isn’t very good. I think the S500 uses a different system, but digital anti-shake isn’t very good no matter how it is implemented.
The FX9 might be a good camera if the LCD brightens properly in limited light – something they haven’t managed to do in any other Panasonic camera. It is probably useable in most situations, but several reviewers complained about the LCD on the FX7 not brightening enough in low light. I find it a bit odd they would produce a camera that isn’t available for sale yet that has outdated movies. But it has a real mechanical stabilization that will aid available light photography.
You can read back through every brand of camera’s threads and find people new to digital who are complaining of their indoor shots being blurry. Consumer film has a wider exposure latitude. And most people have their photos developed at places that auto enhance images that the exposure latitude still left dark. The consumer film camera manufacturers account for that and underexpose after a certain shutter speed has been reached. You can’t do that with digital. Between the lower exposure latitude and people seeing the final product unenhanced, if the available aperture and light require 1/6 second then that is what it uses. Most people can’t hold a large camera steady enough to shoot at 1/6 second, much less a tiny one.
Digital sensors produce more noise with less light hitting them. A given sensor produces the same amount of noise with a given amount of light regardless of which camera it is in. Considering most little cameras are in the f2.8 at wide to f5 at telephoto, you can generate the same amount of light and shutter speed under given lighting conditions with all of them. Some cameras filter the noise out more than others in the processing. One of my few complaints about the Z750 is that they don’t have a setting to turn the in-camera noise reduction off. I don’t find it excessive, but it is apparent at ISO400.
The 5Mp sensor Casio uses in their S500 is the same 1/2.5 sensor used in all the others with 5Mp, 1/2.5 as far as I know. The S500 has an f2.8 to f4.3 from wide to tele, which is better than most in that category of camera. It will do as well as any other with that sensor and better than most at telephoto shooting in limited available light.
Color is subjective. Look at some photos from the S500 and see whether you like the color rendition. Pbase doesn’t have any yet and there aren’t any good reviews out. These are from Casio:
http://dc.casio.jp/product/exilim/ex_s500/gallery.html You might want to wait for some good reviews by Steve and others. The Z750 is my 5th digital camera and I am quite pleased with the colors.
The only two small cameras that will do better than the S500 in low light IMO are the FX9 and Fuji F10. The F10 does it by boosting the ISO and the Panasonic with stabilization. Low light shots are noisier with the F10, but you can capture moving subjects in average light a lot better – stabilization doesn’t help at all for subject movement. And the F10 at high ISO isn’t as bad for noise as other cameras. The F10 is a little bulkier but has the good movies, albeit without MPEG4 so they take a lot of memory space. Neither is as tiny as the S500.
I would avoid the Sony T series. The flash is pitifully weak and the maximum f is 3.5 at wide. You wouldn’t like it for anything but outdoor photography.
One feature on the S500 I wouldn’t want to be without now that I’ve used it is the past movie mode. You can aim the camera and wait for something to happen. When something happens you want to film you start the recording. It records the previous 5 seconds from the buffer and continues to record until you stop it. So you don’t have to grind away waiting for something to happen. The Z750 is the first digital I have used the movies on except to test them when I got the camera. The others are 320 X 240 and almost useless. I’ve been pleased with the movies from my Z750 and would anticipate the S500 is about the same.