Is McDonald's healthier than dominos pizza?

There is no valid answer for your question given the way in which you've Worded it.

1. Big Mac's don't come in multiple sizes

2. Pizzas do come in multiple sizes

As such why the Big Macs calorie amount is a roughly static value. The caloric intake from a dominoes Pizza still has a lot of open variables. Like was the entire pizza eaten? How big was the pizza? What toppings were on the pizza? Was it thin or thick crust? Etc, etc, etc