Yeah it is worth questioning. The major catch in the comparison though is that Xenos is a lot different than R600. The shader core is fundamentally different. It would appear though, from the use of bilinear filtering in games and general lack of anisotropic, that its texturing performace may leave a lot to be desired.
Yep, different but presumably less efficient since R600 is supposed to be a design that evolved from Xenos.
Obviously the edram will play a part though in making the comparison a difficult one.