Because many people may have to work with the scanner, many people will have to learn to use it, so simpler software will result in less wasted time and frustration among museum staff. The only problems may be if you're using a small original to create a glossy brochure. Reliable, in the sense that it will continue to function for years into the future. Flatbed scanners rarely break or jam, but for that extra security go with a name brand that has been in the scanner business for many years, such Hewlett-Packard, Microtek, and Umax. Almost all personal computer scanners are flatbed type, looking rather like a small copy machine.
Flatbed scanners are the best in terms of flexibility and ease of use, and also the least expensive.
Some scanners require you to insert an interface card into your computer. If you have the technical savvy to do this, or have a staff member who can, then it is a reasonable option. However, it's almost always easier to just plug a new scanner into a connection already on your computer. This is a new but reliable standard for computer attachments. Many computers less than 2 years old have one.