We had both meals there a few months ago. The differences have already been explained to you above, so I will give you my preferences.
We preferred the food and atmosphere at dinner. However, BOG lunch food ranks higher in my book than most other QS options. The food at dinner, on the other hand, was pretty average in terms of TS options. For either meal, I would recommend the west wing or rose gallery because they tend to be quieter and more relaxed. The ballroom felt more like a cafeteria to me, it was loud and chaotic.