As far as pic quality goes, the autofocus on the SD110 will be faster then the one on the A75, although using th eAiAF on either is a horrible mistake as it works kinda hit or miss.
The biggest pic quality difference will come from the fact that the S110 will have much more camera shake associated with it. I had an SD100 and man, it was too small and more importantly light to hold still to take a pic, it gave me fits.