My camcorder can take pictures and would use either ratio for images. The only difference that I know is that 16:9 is for widescreen therefore doesn't use the top or bottom.

I once had a film camera that said it was a “panoramic camera”. All it did was just chopped off the top and bottom of the picture.

Just remember pixel count is very important when editing a picture.

Take two pictures, one in each format of the same object. Compare them, zoom both the same amount and compare again.

Pictures are as sound, subjective. What looks good to you is the most important.

3:2 is most common aspect ratio for stills, which is the same as 35mm (24x36mm) 6x4 prints etc, but 5:4 is also pretty common (10x8)