We did both the Storytellers Brunch and Dinner in the few days prior to Thanksgiving. I think of the 2, the dinner is better. I thought the dinner menu was pretty nice, it's certainly the best buffet I've had on a Disney property (though maybe that's not saying much, lol). As others have mentioned the butternut squash ravioli was really good.
Some other things on the menu off the top of my head that i could remember:
braised short rib
pork belly
teriyaki chicken
baked salmon
cocktail shrimp
prime rib at turkey at carving station
popcorn shrimp
pizza
mac and cheese
The characters are more fun for dinner as well with Scrooge / Goofy as Marley / Clarabelle / Minnie / Pluto
The brunch was good too, generally I like brunch at Storytellers. They have usual breakfast stuff like eggs, bacon, sausage, mickey waffles. No french toast unfortunately. I don't remember much of the lunchy items, they had the same salmon as dinner. I think the carving station had the same turkey as dinner I believe, and then some kind of beef (I think tri tip maybe?)
But I think if you're going to do one I'd try to go for the dinner, I think the dinner is only like $5 more