Lunch or Dinner?
Still tough though because I love them both for lunch. I LOVE coral reef, and I always book it right for opening (11:30) so that i can show up 15 minutes early and be guaranteed a table by the tank (if not RIGHT on it, then 2-top directly next to the one that is right on it). I love LTT for lunch too. These are both old favorites of mine that I've been going to for 20 years.
At Coral Reef I have loved the lobster bisque for that entire time... it's what keeps me coming back. It is SOOO good with the fresh, hot, crusty sourdough rolls they serve. On our last trip I had the shrimp and grits and it was delicious (I make this myself and I also had it at Narcoossees as an app and it was nowhere near as good). And the chocolate wave is another favorite I have been ordering for decades... but next time I would ask for vanilla ice cream instead of raspberry gelato, I found it a bit icy. The food has always been very solid for me and I have always been perplexed by bad reviews (I am pretty picky and very detailed in my reviews to show it).
I have not had the AYCTE meal at LTT since the characters were there but the a la carte lunch menu has always been a favorite of mine too. I have not been back in a few years but it still gets good reviews. The atmosphere is also great and themed in there but the backups for seating can get quite large so if you choose that one I'd make it an early seating as well.
If I could only do one I'd probably do Coral Reef just because I think the atmosphere is really stellar and I really love the food as well... but honestly i'd do both... and I actually AM on my next trip!!! Go during a la carte time and share something maybe to keep costs down and hit both for lunch