The camera would have distortions, caused by using a closeup
lens. That can be removed in software, if the software
knows the details of the optics used. Without correction,
it would look ugly.
http://upload.wikimedia.org/wikipedia/commons/6/63/Barrel_distortion.svg
There would also be differences in "depth of field". My scanner
actually dues a good job, even if the book or document, doesn't
lay flat on it. Some scanners are better than others, when it
comes to depth of field, and rendering everything without blur.
http://www.scantips.com/chap3c.html
"The "compact" and "ultra thin" scanners use a very different
CIS chip (Contact Image Sensor). These CIS units are small and
inexpensive, having no optical system (no lens, mirrors, lamp,
and no A/D chip). CIS chips often have LED light sources integrated
in the chip with the sensor. The CIS sensors are full size, extending
over the full bed width. They work by simply being extremely near the
paper being scanned (as "in contact"). This means that there is zero
depth of field above the scanner glass, anything not actually touching
the glass is too distant to be sharp, making CIS unsuitable for scanning
3D objects. CIS is also used in sheet-feed scanners and fax machines
where depth is not a factor."
The camera would be better in that respect.
http://www.carlmcmillan.com/DOF/DepthofField.htm
Paul