Definitely LeCellier!! I had both during my last trip and LC won by leaps and bounds. I know that some people have enjoyed the steak at CR, but to me it was mediocre at best.
I'll be the lone voice of dissent. I had both on my trip last year, and I enjoyed the Coral Reef steak better than LeCellier's. The LeC filet was very tender, but lacked flavor. The CR strip had both tenderness and flavor - YUM!!
I believe the mushroom filet mignon is the signature dish of LeCellier and it is awesome. DH has tried other steaks at LeCellier and he said nothing compares.