Darkcoin's Flaws:[/size]
1) Darkcoin has a 50% instamine by it's own developers during launch, as the block reward was set to 500, and there was no windows wallets/miners. Evan, the developer, and Internetape, the other developer, instamined over 1million Darkcoin's within 24 hours.
2) Darkcoin's name itself, Darkcoin, will always be affiliated with illegal activity like the Darkweb, Drugs, etc, and the name itself ensures that Darkcoin will never reach anything close to mainstream acceptance.
3) Darkcoin's "anonymity" is based on coinjoin, it simply mixes users coins around, making it harder to track it. However, if even the slightest taint if found when mixing the coins, an investigator will be able to deduce who sent what and who received what. The maker of coinjoin, Gmaxwell, deeply criticized Darkcoin since it's coinjoin based "anonymity" is basically a joke.
4) Darkcoin's mixing system/coinjoin relies on something called Masternodes, Masternodes are nodes that are set up by people, anyone can set one up, and Masternodes are the things that mix the coin around. Masternodes also present many risks besides giving trivial "anonymity", if all masternodes are owned by one individual, he will be able to "de-anonymize" Darkcoin and see all transactions clearly.
5) Darkcoin's Masternode Payment system has forked the network many times, and has failed Twice in the effort to pay the owners of Masternodes.
6) Darkcoin's Masternode/Darksend system is closed source, so that means the developers could be stealing coins, or doing any other malicious things, and it will remain unnoticed
7) The Masternodes can always be DDOSed, effectively shutting them down, if the majority of Masternodes were taken offline(they are mostly hosted on Amazon servers), then Darkcoin's trivial anonymity will completely shut off
There are
many many other flaws, it will take up too much space to list, so I've listed the main ones.
Bytecoin's Flaws:
1) 82% instamine by a small group of miners over the course of 2 years
2) Bytecoin devs are shown to be incompetant, they recently tried copy/pasting code from other Cryptonote coins and it resulted in their own codebase getting even buggier than it really is, resulting in users loosing their coins when they sent them in a transaction.
What do Darkcoin and Bytecoin have in common? They were both hugely unfairly mined(instamined/premined), with Darkcoin having a 50% instamine at it's launch by it's own development team, and Bytecoin having a 82% premine over the 2 years it was kept secret by a very small group of miners.