Now, I've heard the Le Cellier has actually fallen a bit since becoming a Signature restaurant, which would be disapointing. However, having never been to the Yachtsman, I don't know which would be best.
All the bad comments I've seen about signature Le Cellier are from people who haven't been there and have no plans on going there. All the actual reviews point out that the food has improved, and if you liked the atmosphere before you'll like it now.
Here's the real deal with why people don't want to go to LC for dinner. Most of the people who go there liked it because it was a steakhouse for 1-credit on the
DDP. I'd go even further to say a lot of these people ordered almost the exact same thing: cheddar soup (which is tasty with the pretzel bread), mushroom filet, and a dessert (maple crème brûlée, chocolate moose, etc). For dinner, these people would still probably order the same thing, but now it would cost twice as much on the DDP, making dinner a worse value than it was.
That doesn't have anything to do with the food quality at all. I've had three dinners there since the change, and all had great food and service. The menu provides more options than Yachtsman for non-steak fans (I loved the duck, cod, and salmon), while Yachtsman is mostly big, plain steaks with some sauce and potato. Le Cellier still has great steak options, including the filet, rib-eye, and New York Strip, but if you want a porterhouse, only Yachtsman has that (and a lot of people seem to order it).
So it really depends on what you're looking for. Yachtsman might be a better choice if you want a big piece of steak. However, I find Le Cellier's menu to be more interesting. For the record, before the menu change I wasn't a fan of LC at all, and I'll openly say I had a terrible lunch there. But I really think the food has improved a lot for dinner. People just don't want to give it a chance, and that's understandable. I've had mediocre meals at Yachtsman, Flying Fish, and Citricos, so I'm reluctant to go back to those places despite their popularity here.
Here's my pics of LC dinner:
http://www.disboards.com/showpost.php?p=40232644&postcount=275
http://www.disboards.com/showpost.php?p=40246955&postcount=290