Share 'What's the best way to scan and save vital records'

I'm scanning a whole stack of vital records.  How should I save them?  Should I scan and save them as photos (.jpg or .png)?  Of should I scan and save them as documents (.pdf or .rtf)?  I know they'll be much smaller files if I scan them as documents, but I have plenty of storage space so I'm not concerned about file size.  What I am concerned about it quality, and which way is the best way to d…