I've done both and prefer Teppan Edo. These are 2 very different restauraunts... having done both I would choose Teppan Edo. I did not care for Coral reef. However.... in your case, trying something new is always fun too. Food opinions on Coral reef are very split... so I can understand why you are hesitant.
Good luck with your decision
I have to go with Coral Reef.
We have been to Coral Reef twice now, and it was very good. In fact, it is now my husband's favorite restaurant at WDW and he insists we go back every trip.
I, unfortunately, have been spoiled by Benihana. I cannot go to any other hibachi now, and I have tried a few times. So Tepan Edo doesn't hold that much appeal.
We have been to both several times and we enjoy them both.
If you have been to Teppan Edo I would definately give Coral Reef a try. We love the Mahi Mahi, NY Strip and Creamy Lobster Soup.