At a general level, calories are equivalent. Calories are a measure of heat when the food is completely burned in lab. The body does not process all foods equally. Cells prefer to burn glucose (sugar) & carbohydrates first, and will store fats for use later (if glucose levels are sufficient). Apples are higher in sugars and will tend to be used as an immediate energy source. Tacos, being higher in fats, will tend to be stored as fat. Foods also have different tendencies to change blood sugar levels (glycemic index) which affects whether they will be burned or stored.
But as long as your caloric intake of any type of food is less than your caloric expendature, no problem. Difference between sources of calories is not great enough to worry about for most people. It's the fouth taco that is the problem.