Well, if the need is urgent, you are confined to the choices in front of you, but I've never used either so I can't help on such a choice; but from all I've heard, both of them are not that easy to use and require careful handling and maintenance. If you are not in a panic to buy, I'd suggest some market-watching and, depending on how familiar you are with drum scanning, adequate research into useability and what it takes to get repeatedly good results from them. People who offer drum scanning services normally charge quite a bit for them because of the work and experience involved.
Effective resolution is a bit elusive. There is a real distinction between technical resolution (i.e. stated pixels per inch of capability) and the optical sharpness of the scan. What the scanners are rated at and what they actually produce are usually not the same, the latter being lower than the former because of optical limitations; I've heard the two models you are considering can produce some very sharp output. Much also depends on what size prints your clients want from the scans. If you are planning to print a full 44 inches, I agree you need high resolution, but you also need sharp results. I hope you have a way of testing these machines before buying.