Hi, new to the forum and fish tanks, just bought 55 gal for SW coral tank - good friend of mine is very knowledgable and talked me into it.
Anyway, I took a look at your links - I just bought a Canon not to long ago and love it, it's a bit overkill for a point and shoot, but I'm a camera nut - it's the G9, has an incredible macro and some additional features as well (ability to mount external flash, lenses, etc)
Not sure about the macro on the 2 cameras you listed, but noticed they minimum focus at 1.2", whereas the G9 and also the PowerShot A650 IS focus as close as .4" I took a pic of a quarter and it filled the screen, plus they are 12 megapixels. Highly recommend these cameras. Also, they do not take accessory lenses from what I could tell in the specs.
I would take a look at them and this place bhphoto, they are the real deal and usually have fair prices. Easier to do comparisons there vs canon website.
Powershot A650 IS
Here's a link to some pics of my friend's tank I took just messing around - with proper lighting and less beers, I would feel confident I could capture the fish with no motion blur.
G9 test pics
They're compressed for web, the originals are much larger, croppable, blow-up-able(?)
Hope this helps,