They are identical except for the larger LCD and the lack of a optical viewfinder on the SD630.
When you put a 3.0 inch screen on that small camera, there is not enough room for a viewfinder.
Picture quality should be identical.
Here is the press release:
Which one is the best?? I've read that Canon 630 has no viewfinder, anyone know what is that for? Also, Sd630 has bigger LCD screen though, what is the big deal?? what about picture quality ??? thanks a lot.