If you have to choose, I don't envy you your decision!
Each restaurant is different both in style and substance. I suppose if I was told I could only go to one or the other, it would be Le Cellier--although I love Teppanyaki equally.
I would choose Le Cellier over Teppanyaki for a couple of different reasons. First, I can grill my own meat, vegetables, etc in the Japanese style. Although I can also grill a mean steak, I cannot duplicate the pretzel bread, cheese soup combo!
My husband swears the steak at Le Cellier is one of the best he's ever eaten. I, personally, prefer the tenderloin salad and cheddar cheese soup with the breads. Our son loves the chicken sandwich, soup, and bread. Le Cellier's bill has always come out less than Teppanyaki, too. We've found the service to be very good at Le Cellier as well.
The downside of Teppanyaki, hence the sway to Le Cellier, dining with others--it's a luck of the draw thing--we've had great table mates and those who wouldn't speak. Likewise, we've had great teppan cooks who were quite animated and made this an entertaining and yummy experience. We've also had some who barely spoke and had no skills other than cooking.
All of that said, I love the lobster, shrimp, and scallops at Teppanyaki. . .maybe I should change that vote. . .