Unless you're desperately tight for space, I would recommend you remain with a flatbed scanner, if possible. I've never been a big fan of roller-fed scanners, as they tend have alignment issues eventually, as inevitably one set of rollers degrades at a different rate than the opposing side, causing the page to skew as it is fed. When you place a page on a flatbed, it remains as true and square as you place it, every time.
$0.02
