You can compare these two spec sheets on the v30 and v33. The only thing that jumps out when I looked at them is that one has OCR (Optical Character Reader) software. They look the same physically.

My personal preference was the V500. The lid opens up with a hinge on the short edge rather than the long edge. It appears to me to be more ruggedly built. That's the one I bought a couple of years ago and it works fine for either text or 3D object scans. You can usually find one available refurbed by Epson on their site for under $100. They also have a v30 for about $50.

http://www.epson.com/cgi-bin/Store/jsp/Product.do?sku=B11B200201

http://www.epson.com/cgi-bin/Store/jsp/Product.do?sku=B11B193141

Clearance store site:

http://www.epson.com/cgi-bin/Store/BuyEpson/ccProductCategory.jsp?BV_UseBVCookie=yes&oid=-13268