I am one to go for service. Of course, food quality has to be of a good standard, and I will choose a restaurant with average food and smiling waiters, than a restaurant with excellent (and probably exorbitantly expensive) food but a waiter with the terrible i-hate-life face.
The underestimation of the value of the smile is an indication of lack of care for customers, no matter how the company writes how it values customer relationships.