With this model, we feel that projects like colored coins and metacoins like mastercoin will have a much easier time building on top of Ethereum than Bitcoin.
I'm afraid you're missing the point of colored coins and mastercoin: they are supposed to extend functionality of Bitcoin.
Obviously, smart property, user currencies and decentralized exchanges can be implemented in a variety of ways, but there is a significant demand for things like this specifically from Bitcoin community: people who already own bitcoins and want to trade using bitcoins.
Decentralized exchange/smart property applications on top of Ethereum might be awesome, but it's not same thing as colored coins and matercoin.