Teppan Edo's food is very good, but yes, the meal is mostly about the "show".
Nine Dragons was ok.....pretty much Americanized Chinese food.
If I may throw another choice at you....Tokyo Dining. It's in the same building as Teppan, but on the right hand side instead of the left hand side of the second flood. Try to get a window seat, or at least closer to the windows so you can eat and gaze out over the lagoon. And the food was quite excellent....not the show that Teppan Edo is, but the food is better quality and taste and the servers are just wonderful. We ate there 3 times this last trip, lol.
Just FYI...many people avoid Toyko Dining because it's billed as "sushi"....but the fact is that is only half their menu.....the Tempura is excellent, and they have combos with Tempura and meat. They also have steak and chicken, and while I didn't try those (being more of a Tempura and Sushi type), a dinner companion said the steak was more tender than Le Cellier's....with a more subtle, steak-like flavor. He loved Le Cellier....but felt that the taste was about the marinade not the steak.
If you like Sushi it was very high quality, and there are many combinations to choose from as well as ala carte. Not quite as many choices as a top notch sushi restaurant, but enough to satisfy a sushi lover that doesn't want only run of the mill selections.
Now...if you're set on one of the two you listed....I'd go with Teppan Edo....the food quality was definitely better than Nine Dragons and the show adds fun to the meal. I was so hoping that after the long rehab of Nine Dragons that it would be something worthy of such a great country. I realize that many think they need to fit their food to an American palate, but couldn't they have had a few true Chinese dishes for those of us who appreciate their native food? Having spent many years in China, it was very disappointing and not a single thing on the menu that I couldn't get at the take out place in my hometown. They should have taken the same approach as France on the other side of the lagoon....they have a few very French selections to represent their true cuisine.