What? That is the purpose of measuring. Then an exact correspondance of the functional part means they are the same.
Apples to Apples and Fruit baskets to fruit baskets.
Which is exactly what I'm talking about - break it down into the smallest functional parts and compare those, so you have analogous functions in hand, and do it one at a time. Otherwise, you've got chaff in your wheat. Then, you turn around and look at global comparisons of collections of functional subunits. Bottom-up, not top-down.