What is the best text to speech with OCR function?
If you have the money, you could use OmniPage by Nuance here: http://www.nuance.com/for-business/by-product/omnipage/index.htm. Makeuseof has covered some free programs:
You can look into 1SpeechSoft at http://www.1speechsoft.com/
I think this the best one.
You can look into NaturalReaders at http://www.naturalreaders.com/
I don't know about "best", but the standard software for OCR with speech synthesis are Kurzweil 1000 and 3000 (see http://www.kurzweiledu.com/products.html). It's used to enable those with visual impairment to read printed books. Kurzweil has been making such software for decades (I rememeber hearing about them in the late 80s) so they must be doing something right...