Ok so on paper Peercoin might be have some better features, but why should I use it instead of Bitcoin?
You probably wouldn't use it but the crypto-economy in general would use it to make small numbers of extremely large monetary transfers.
That's what it was designed for. To be a monetary backbone - and before you say "why can't I just use Bitcoin for that", it gets technical and has some economics criteria thrown in. Suffice to say, it's one of the coins that had a lot of thought put into the role it would adopt in the crypto-economy.
Have a look at this video:
http://www.youtube.com/watch?v=ynwz8H66chYThat is now almost a year old and Peercoin is STILL in the top 4 marketcap coins. That is amazing and is not due to being "kept up there by traders".. If DRK can do that in a year's time it will be in with a high chance of being here for good.