The dwarves will use the closest table to wherever they picked up food, regardless of whether it was the table the room is designated from or not. This means that they're all given equal priority.
The tables in the furthest corner from any entrance into my dining room seem to have the most activity for me...
Though on second thought I think these tables might be the ones directly under the food stockpile, so dwarven measurements might actually put them closest to the food. I'll have to observer them a little more closely.