I remember informative article regarding comparing PIVX, Zcoin and Monero.
Couldn`t find it now..
It was explaining why it`s illogical that PIVX is so cheap compared to that 2 coins..
At least you should have more specific key words for your searching procedure.
More specific your key words are, higher probabilty your chance to find what you need.
Just my guess, privacy/ anonymous is the most common characteristics between them, but I don't think it is what you are looking for.