The Canon S45 is 4 megapixel and has a 3x optical zoom.
The canon S50 is the same but is 5 megapixel.
How? digitally? Ignore any mention of digital zoom - its a complete marketing gimmick. Optical zoom is the only thing that matters, digital zoom is just the same as resizing the photo in an art package.
Minimal focal distance on the S45 is 10cm (3.9") in wide angle macro and 30cm (12") in telephoto macro. And thats without spending more money on 'special lenses' :p