We've done LeCellier for dinner and for lunch and prefer lunch much more. They have sandwiches which are perfect for a nice meal in the middle of the day. Besides the food, though, the pace at lunch is more laid back and definitely less hectic. We felt rushed at dinner, not because the servers were rushing us (they were fine) but because there were mobs of people waiting outside and inside for their tables. It's difficult to be able to enjoy your meal knowing there are people anxious for you to leave (not the wait staff, other guests).
It's just so much more relaxing at lunch. I'd go back for dinner only if someone else in my party really wanted to.