How much will a directory's pagerank be penalized for using common category dumps? Also, how does the use of those mysql backups affect your decision to purchase a directory? Thanks in advance!
There is a possibility that G may penalize those similar directories in the future, even to their PR. But I doubt they penalize a directory for that reason only. I would suggest though that you should make your directory as unique as possible. That's what G wants anyway. It's not really a duplicate content issue, but it sort of relates to that I guess.
Not everything is about PR It just shows submitter how much effort you have done ... You should use category structure that "You" think is best for your directory. Having a better category structure with unique touch is always a big +.
A cat dump should only be to seed your directory. As submits come in, add new cats to expand and tailor your directory to your needs.