We just did both of these places last weekend. Bistro was outstanding. Chefs was blah. It's amazing how different our experience was - especially when considering that only about 30' separated our two tables. I'm guessing the food comes out of the same kitchen, but what a difference there is.
I will say that the Bistro was certainly much more expensive. Not out of line though. It was ~$200 for two, with wine. The food was outstanding from appetizer to entree to desert, both in presentation and taste.
Chef's was much less expensive. Only $90 for two, but without wine. The chicken had no flavor and the vegetables had been cooked for a month and a half. The braised short ribs were ok, but not great. A table mate had shrimp that was absolutely tasteless (confirmed by a diner at an adjacent table who had the same dish). Even the creme brulee for desert was poor, as was the chocolate cake was dry and didn't have much flavor.
It will be a long time before we go back to Chefs for dinner. But, we did have a good experience for lunch there. Very strange.