Big size documents: digital back vs scanner

Hello,

I got to photograph a series of big size documents (60 X 80 cm) in 300 dpi.
What is the most appropriate equipment: a digital back or a scanner? The
scanners (Scando of Kaiser for instance) are much cheaper but what are their
scanning time for A1 format in 300 dpi? Has someone any experience with that
kind of scanner?

Thank you for your information about this.

Daniel
Paris