We have done both the Superstar Character Breakfast and RPR, we prefer RPR. I am a bit biased because we did the Superstar in 2012 and it was NOT a buffet at that time. Also, I hear the price is increasing. For $25, you get a tremendous buffet at RPR (it is so good, I miss it already, and just had it two day ago) and great character interaction. I thought the character interaction at both locations was tremendous, so it boils down to food and price.
However, the Superstar is right in the parks, so when you are done, you are literally steps away from the action. At RPR, it is just a short boat trip away.
So, it boils down to location vs. food/price. Can't go wrong either way