When I purchase my sander, I debated between the 3 x 21 and the 4 x 24.  Looking back, I'm glad I purchased the smaller of the two.  For a much lower price, I got a belt sander that handles all of my rough sanding  needs.  The 7 amp motor is extreemly strong and handles quick material  removal with ease.  I like the swiveling dust bag and the cord on the top  of the handle.  This keeps the bag away from your hands and the cord up off  of the work surface and away from the sanding belt.  Overall, I got even  more for my money that I originally thought.