Canon vs Kodak jpg file size very different

I have a Canon S400 which is 4 megapixels. A friend just purchased a
Kodak CX7430 which is also 4 megpixels.

We both use what appears to be the "best" quality settings. I take the
same shot with both cameras.

Both cameras produce an image size of approximately 2200x1700.

On download from the memory card(s) to the computer however, each camera
produces a radically different size jpg file and the larger, of course,
seems to produce a more detailed picture.

Canon - 1743kb
Kodak - 736kb

Why would two cameras, both with the same number of pixels, both
producing a very similar image size, then produce jpg files of such
totally different sizes?

TIA

Louise