My little rant on portable document scanner
Where portable scanners drop the ball a bit is with regard to the quality of the image. All things being equal, a larger desktop scanner will give you a much clearer image than a portable scanner. That being said, a portable scanner is still an invaluable aid for most common business applications, and the fact that they are so small and portable makes them the best possible choice for mobile scanning use. If image quality is of more importance to you, you will want to look into a portable scanner that has a high dots per inch or dpi image resolution. If you intend to be doing a lot of photo scanning and want to resulting images of sufficiently high quality, you will want to get a portable scanner that offers 48 bit depth.