I think this is a good reason why closed and open headphones really can't be compared on any common playing field. Either one will be better depending on the circumstances.
I like my CIEMs a lot, but switching from them to the open back full size HE-6 makes a dramatic change in listening experience. A closed full size would be more like in an apples to apples comparison with an open one.
That is a very good and fair statement. However, we can't help it but keep comparing HPs to one another, regardless they are closed or open. What else would we do on head-fi, right?