To use starter culture, or not to use starter culture?

[cheesebrough]

I've seen different recipes for producing mozzarella cheese with pasteurised cows milk.
But i can't really figure out the advantages/disadvantages of using a starter culture for lowering pH vs using citric acid for lowering pH?
Does it make a difference?

[Sweet Leaves Farm]

citric acid works much faster, while starter culture has more flavor.