The NOOKColor can buy from any epub store. It is more tightly locked down at the Andriod level but it is trivial to buy from any epub store, both with and without DRM.
The NOOKColor has an excellent screen and the SDK is downloadable from here -
http://nookdeveloper.barnesandnoble.com/tools# (login with your account). I haven't seen the Cruz's ereader SW but the NOOKColor's reader sw is superb. It is better than any of the products I have seen to date, it is fast and a joy to use. It takes advantage of the touch interface and the CPU. I love it.
The NOOKColor has a better screen with 1024 x 600 resolution as compared to the 800x480 of the cruz table. The ram and cpu are comparable. The NOOKColor is more locked down but does run a later android (2.1) and has been rooted. The root kit is reversible and due to the order the NOOKColor boots up it is effectively unbrickable. B&N promised Andriod 2.2 in 2011.
To be honest, unless I really wanted more video codecs right away, I would choose the NOOKColor. And I did. I absolutely love the reader sw on it btw, and if you plan on reading on the device I really recommend the NOOKColor.