Hi Vicky,
To be honest the main difference between Cinderella's Royal Table which is inside the Castle at the Magic Kingdom and Akershus Royal Banquet in Norway in Epcot is the location.
At both you get to dine with the Princesses, they tend to be very similar with Belle, Snow White, Aurora and Jasmine often at both. Cinderella is guaranteed to appear at CRT whereas at Akershus she only might be there. You get a photo package included in the price at both but at CRT the children also get a wand for girls and a sword for boys, there is also a very cute wishing ceremony.
The breakfast food is quite similar but the lunch and dinner foods are pretty different with CRT being more traditional and Akershus being Norwegian. You can see the menus at
www.allears.net by clicking dining then menus.
At breakfast there is only about a $6 price difference between the restaurants for adults and $7 difference at lunch time but if you're on the Disney Dining Plan CRT is 2 table service credits whereas Akershus is only 1 credit. Both restaurants are popular but CRT books up incredibly fast and if that is your choice please make sure you call 407-939-3463 at 7am EST at exactly 90 days before your trip.
I personally think if you can afford it CRT is a must do at least once, but my children actually preferred Akershus. Sorry that wasn't much help was it!
I hope I've cleared a few things up and whichever you choose I'm sure you'll have lots of fun,
Jo