Have you done the Ratatouille restaurant or Plaza Gardens Donald Ducks Wife ? How would you compare it to those, characters aren't important to us this time, so it really all comes down to whether the food is worth the extra spend.
Restaurant des stars (ratatouille) is our favourite, we ate there 3 times on our last trip(8 nights). It's the best 'normal' food buffet we have been too. When I say normal, I mean its not full of sea food and strange looking cheese's, which we are not use too. We like to fill up at buffets while we are away, and restaurant des stars is good for that, as it's meats, salads, pasta, pizza, and the desserts are amazing!! It feels like a nice family friendly restaurant.
Plaza gardens, we have only ate at once (same trip as above) we were not too impressed, again for the sea food etc
It just depends what you want, if you want sea food and local type food, then plaza gardens and the sunday brunch is great, but for me, I'm a down to earth girl, who just wants her tummy full so I can go enjoy the parks, and of course eat food that I know that I enjoy, then it's restaurant des. Stars.
But that's just my opinion, maybe others have a different perspective