Separate And Unequal

Suppose a person has two esrogim, an inferior one that is definitely kosher and a beautiful one of questionable validity (it may have been from a grafted tree). Upon which esrog should he recite the berachah on Sukkos morning? Rav Chaim Brisker ruled that he should recite the berachah over the esrog that is more beautiful and subsequently replace it with the inferior esrog. If the beautiful esrog turns out to be kosher, he has fulfilled the mitzvah in the most mehudar fashion. If it’s not kosher, he at least still fulfilled the mitzvah with the inferior esrog. Whereas if he first holds the aesthetically inferior esrog, he has definitely fulfilled the mitzvah in a non-mehudar fashion. The fact that he later took hold of a beautiful esrog is of no regard. He already fulfilled the mitzvah; what can possibly be gained by holding a beautiful esrog now? It’s meaningless.
The Gemara in Eiruvin discusses a situation where someone has a doubt regarding two of his animals. One should be brought as a sacrifice for ma’aser beheimah and one should be brought as a korban shelamim. Since we are unsure which one is which, we offer both animals as sacrifices in exactly the same way.