A digital camera gives you more flexibility for adjusting resolution, exposure, white balance and macro mode options. Moreover, holding a camera is easier than holding a laptop especially if you have an item that needs photographing from different angles. Laptop cameras can be grainy and you have far less control over lighting and balance, the resolution could be very low too. If you really want to document things well then I would use a digital camera. In the collection where I used to work we could only afford a cheap digital but it was enough to take good documentation photographs, I found the macro mode invaluable for small labels and things like that.
