I was on the Star for an Alaska cruise, but I have recently done the Mexican Riviera on both Celebrity and RC. One of the good things about your cruise on the Star is the length of time in ports. It is nice that the itinerary has you staying late in Acapulco (since nighttime is when this city really gets revved up) and a good portion of the day in Cabo (make sure to spend some time on Mendano Beach and order the fish tacos at "The Office" - on the beach). Check out the information on both of these ports at PortReviews.com
As for comparing Royal Caribbean and NCL - I am afraid NCL doesn't quite measure up. The Star is absolutely beautiful and the staff for the most part were very helpful and friendly. The problem with NCL is that it lacks consistency. While the public rooms are impressive, the cabin was quite small and unimpressive. The food is another prime example: Since we ate most of our evening meals at the specialty restaurants, the food was great. On the few occassions we ate in the main dining room(s) - it was a major disappointment and I did not choose to repeat the experience. However, the fish and chips at the Red Lion Pub and Blue Lagoon were a major bonus; the sushi was the best my friends had ever tasted at sea (I can't attest to that since sushi is not my thing) but the burgers may have been among the worst. I could go on an on, but I think you get the picture.