Saying that there's a difference is a tautology. Of course there's a difference. There's also a difference between someone trying to decide between getting an a

Saying that there's a difference is a tautology. Of course there's a difference. There's also a difference between someone trying to decide between getting an apple or a blueberry danish. The important bits are whether the difference is detectable in a manner that is convenient (putting each passenger through an MRI machine is out of the question), reliable (minimize false positives and false negatives), and so on. Just saying "there's a difference" adds no new information to the conversation unless you're able to expand on the quantifiable aspects of those differences.