I dont think putting down other legitimate coin projects is a smart thing to do. Both Darkcoin and Monero are fully open source and honest efforts.  I support DRK for many reasons, the lower emission curve and the incentive to hold through masternodes make it at least in the mid term a safer investment.  Monero is at the moment a highly inflationary coin, although a solution to that may be found in the future. Darkcoin is a deflationary coin with a low block reward that is reduced by 7% each year.

Also Darkcoin ceased to be a coin which only value added is anonymity, we are working hard to add fast confirmation transactions too, private testing has been successful and public testing should start soon. We are estimating around 20 seconds confirmations on main net.  This can have amazing implications for betting, so making it a unidimensional comparison about anon is no longer appropriate.

Finally, Darkcoin uses the exact same Bitcoin API and Bitcoin code base, so if I am deciding on a coin to add to my service right now, I would definitely add Darkcoin over Monero.  Just because Monero uses a completely different codebase (Cryptonote) that hasn't endured the test of time yet and there are some basics things missing like an official GUI wallet. So if you are offering a service that is focused on the public at large, people are probably going to find having to use a CLI to be an obstacle for adoption.  This is why I dont consider Monero a direct competitor for Darkcoin and wish the project the best,  but they still have a long way to go and are definitely not ready for wider adoption yet. I think that also shows on the market cap  DRK market cap is approx. 5x that of XMR

Darkcoin has also been featured on mainstream media and might attract new customers to your site, not only Darkcoin community members, but outside users interested in trying Darkcoin's features that they saw on Wired.com or Bloomberg. So from a business perspective I think adding Darkcoin is on your business best interest, I would also keep an eye on Monero to see how it evolves and consider it at a later date.