Speed tends to be on the top list of many businesses when considering the type of scanner to purchase. Most people believe that the faster the scanner, the better it is. However, finding a proper scanner takes examining features other than just speed.
One thing to consider is document sizes including A4/legal, A3 and larger than A3. Consider purchasing an A3 scanner to handle irregular sized documents when needed. The type of scanner comes into play as well, since a feeder scanner can feed longer documents while a flat bed scanner is limited to the size of the scanning bed.