Im looking at the same cameras. I currently have the SD300 and before that the S410. I would love the extended MPEG4 movies on the canon. Right now I get about 8 min of vid on the 1 gb card. The images off the canon are awsome right off the bat, the casio lags a little bit but from what I have read in all the reviews with a little in camerea tweaking from the defaults, its pretty good. Also, think about what you do with your pics, how many 8x10's do you make. I have close to 3000 4x6 and have printed maybe 5 8x10s since I started taking pics. A digicam from 4 years ago with 3 meg would be fine for that. People lose sight of the fact that printing at 4x6 and 5x7 and viewing on screen are two entirely different beasts. If you arent printing large sizes, you will not see a difference.
But, I am holding off on the casio until they have the lens error thing sorted out. I have seen to much complaining on forums about this issue.