Problem with COR is that they don't know how to update (encode). They still use x264 build 532, which is very old and when comparing it to the latest builds, its output looks pretty shitty.
In other words, if there's another group like arigatou, e-d and such doing it, it's best to wait for them. Not that E-D looks so great for this one, looks like they smoothed too which caused banding, but they have more detail than COR does.