Different animals, but both nice. The Panasonic has a greater variability with the 20x zoom and a good lens for this category. This is the prototypical point and shoot camera for 'every situation' - not brilliant in any of them, but 'good enough' if you just want a simple, portable camera for all occasions that has 'decent' picture quality. There is a smaller zoom range on the Canon, but the sensor is larger which results in a better overall picture quality. The lens is also faster which is is not important for the knife pics, but can make the difference for people (or dogs) in motion and will be an advantage in lower light situations. You should compare the Canon 100S more to the Panasonic LX5 or the Olympus XZ-1, they are in the same category. I would see those three as advanced cameras reg. picture quality and controls when compared to the TZ30 (which is called ZS20 in the US).
All that said, if you only use them for Web pictures or small prints, the picture quality of either one of them will be just fine. Where the advanced ones start shining is in larger prints and more control over individual parameters of the picture.
Stefan