I have heard that the k70 has a lot of key ghosting if you are a very quick button presser. If you really care about colors and backlight that much then it might be a good option.
The model S is a very expensive keyboard, while nothing is really bad about it, its a bit pricey for what you get.
Haven't gotten any negative feedback about any of the CM keyboards that I have ever reccomended, and the XT seems to fit in there pretty well.
If you haven't looked into ducky keyboards, I would recommend it.