Remember for Shatabdi only the Executive Class is 2x2 otherwise the normal class is 2x3. Also just watch out there is also a thing called the Jan Shatabdi, I'm not sure whats the difference having never traveled on it, but I do believe it lacks AC but I could be horribly wrong.
Shatabdi/Rajdhani in general are the way to go, unless you are looking for a typical Indian experience