A. I can appreciate shoppers seeking buying advice, but I don't sell scanners, so I don't have such advice to offer. My intent here is about scanning tips and basics, which is hopefully applicable to whatever you purchase. Mac or Windows is the first choice to make. The SCSI and USB scanners are the same hardware units, but the software and drivers are not the same. Some few models bundle both sets of software.
Flatbeds are the best, most versatile, for photo prints and documents.
Sheetfeeders are becoming rare, and I don't think you can buy a handheld scanner anymore. The only disadvantage of a flatbed is the size and table space they need. Film scanners are extremely desirable for 35 mm. Film is the first generation original image, there is no way to get better results than from film. Generally the reflection from the lower lamp ruins image contrast from film, but it is not as simple as turning it off, the CCD needs to be calibrated from the upper lamp too.