One of them is an academic paper and the other has a website that mostly consists of "coming soon" pages. But seriously, DarkCoin appears to use CoinJoin[1] which has a smaller anonymity set than SNARKy systems.
Darkcoin has actually implemented a lot of new code. They have an advanced form of decentralized coinjoin called darksend mixed with a system of masternodes which share the block reward as a sort of proof of service. The masternodes require 1000 DRK ($6600+ as of right now) to limit network chatter and make it increasingly expensive for people to take control of a lot of masternodes. Additionally coins in masternodes are removed from circulation, allowing a sort of positive feedback loop as far as price goes.
Darkcoin V2 is also adding ring signatures mixed in with the masaternode system so I'll see how that works when it gets released.
[1] https://bitcointalk.org/index.php?topic=279249.0