Finereader is very accurate-- though if you choose to embed the text in a pdf, Finereader doesn't allow you to review and edit the detected text before embedding it in a PDF-- which means that it's a royal pain to correct the errors that do slip through.
Finereader Pro supports a good many additional languages over the Express version-- Arabic, Chinese, Japanese, a slew of computer languages. German Fraktur is still missing, and so is the option to train the engine on your own documents and typefaces. I'm not sure what the limitations of the Finereader for Snapscan version are. Also, if you buy it from stores other than Apple, it goes on sale periodically.