+1 on everything. In my sphere the XML HD was around 740, give or take, and the XML2 is around 950, give or take. It's difficult to say that you can really "see" the difference in brightness, but there's definitely more discernible throw. As TWL says, more of everything - with one exception on mine - there is LESS greenish tint on my XML2.
I have the cool XML2 HD, and I previously had the cool XML HD.
Very very similar. The XML2 just has more of everything that the XML had. That about sums it up.
I sold my XML HD because I could see no reason to have 2 lights which were so similar.
I could easily have lived with the XML HD, but the updated emitter gives you more, so I upgraded.