it is not about size
it is all about the RIGHT one!
Scanback 6000 xp has a smaller resolution, but is one f-stop faster (larger pixels on the same size CCD)
Scanback 8000XP has a larger resolution but is one f-stop slower (more pixels on the same size CCD)
XP Models have the new higher sensitivity CCD's from Kodak that add lower noise, improved tone depth and double the sensitivity of previous Kodak CCD's. This allows you to scan faster, use a smaller f-stop or half the light previously needed. All the XP models have the extended resolution feature giving you up to 538MB in 24-bit.