Buffing pads are available in all sorts of diameters.  Other than the obvious size discrepancy, expect to see a change in polishing performance as you outfit your machine with small or large diameter pads.  

When choosing any pad, keep in mind that in comparison to a large pad, a small pad offers:

• Less total surface area
• A decrease in edge speed for any given RPM
• A concentration of applied pressure and polishing force

I am currently working on a page that delves into the subject.  Until then, take a look at the charts below.  They show linear speed and surface area comparisons related to using small and large pads: