For me, it is a question of precision and timing. There are two primary factors to be considered in the buffet breakfast protocol scenario.
One - how large is/are the plates, and will cereal be partaken of?
Two - beverage consumption. In other words, are the orange juice glasses/coffee cups of sufficient size to not require replenishment during the mastication process, or will they require topping up mid-plate? In such a scenario, two trips are better. On the other hand, one larger plate or two smaller ones may be desirable if the coffee cup/glass will not require replenishment for some time.
Thought and planning is required for these things - you can't rush into a buffet breakfast willy nilly...