Optical Density
The optical density of these two photo scanners differs slightly. The V500 has a 3.4 DMax optical density and the V700 has a 4.0 DMax optical density. The higher the density, the clearer the photo, essentially; thus, a large-resolution scan at the same dpi will be slightly clearer with the V700. This accounts for the smaller pixel resolution of the scans, as the photographic information is a bit more compressed. The downside to this is scans from the V700 can't be enlarged as much as those scanned with the V500.

Read more: Differences Between Epson Perfection V500 & V700 Photo Scanners | eHow.com http://www.ehow.com/info_8035171_dif...#ixzz1bQg7ccdA
Saw this today and it reminds me why I always tell students the internet is great for learning how other people think, but facts and figures often lack the rigor of fact-checking.