The passphrase approach is simple enough for the SQL stmts, and it might even peform better (I haven't measured, but for sure you don't have the overhead of opening a key).  The only problem is handling the passphrase.  Where are you going to store it? 

If you're encrypting data to achieve regulatory compliance or some other serious purpose, then you probably won't want to hard-code the passphrase within stored procs or application source code.  And you won't want to store it in a config file or the registry as plaintext, it would have to be encrypted....  The approach published here just basically solves this problem, you don't have to worry about protecting the passphrase. 

If you can get away with hard-coding the passphrase in your code, then that's the easiest way to go.