Finereader works best at 300dpi - tests I carried out some time ago using various flatbed resolutions confirmed this - and at around £100 I think it is the best value out of the box solution. I did quite a bit of work using another of their products - FlexiCapturePro - as structured text extraction is possible, and I was looking to create an automatically populated database of information - the project ended up as http://www.radiotimesarchive.com
and straight forward text embedded PDFs. Talking to the UK ABBYY team, I believe that colour information is also taken into consideration with FCP, but I am not sure if this extends to FineReader, which is a slightly different engine IIRC.
Acrobat is fine for most things if you already have it, but I certainly wouldn't recommend buying it just for OCR as it is hugely expensive in comparison with FR11, and has some strange quirks on some settings. I have just upgraded to Acrobat X and the batch processing is superb but, as someone pointed out on another thread here and on some other forums, it seems to introduce some weird spac ing pro blems which can cause word searching to fail. I am just testing FineReader 11 Corporate edition to see if the batch processing on this does all I need, although I believe only Recognition Server (serious money) will output to multiple file types at the same time, so if you want text embedded PDFs, XML and plain text, you will have to run jobs several times using FR. ABBYY FotoReader was a separate programme at one point, but I think is now bundled within FR and I know that early experiments a few years ago with that and phone camera quick point and click images were impressive.
The bottom line with any OCR software is the better the original image, the better the results. One thing to remember is that if you are scanning to a compressed format, any processing is likely to introduce additional artefacts which could cause different problems. All of my scanning (via flatbeds) is done at 300dpi and usually to TIFF.