The imaging engines are probably the same in both cameras, but the A80 is much more of a photographer's digital P&S while the IXUS/Digital Elph is a small, stylish multimedia accessory.
Both cameras will most likely return images of the same "quality", but the A80 offers much more flexibility and control over the image-making process. The 430 only has Program AE and manual exposure modes while the A80 offers those as well as shutter and aperature priority AE. Also, the A80 accepts telephoto and wide-angle lens additions and the ability to use 52mm filters or close-up lens. Finally, the A80 uses AA size batteries (I would definitely suggest rechargables), and it's always nice to know that your power source is ubiquitious.
These are both great cameras, but they're aimed at different market segments. If size and weight is the deciding factor then the 430 is the way to go. However, if you're willing to carry a slightly larger and heavier camera as well as some accessories you're going to get a lot more control over your images with the A80