Bava Batra 35 - July 30, 24 Tamuz

Two people claimed they had each inherited a particular piece of land from their fathers. Rav Nachman ruled that the stronger one prevails. How is this case different from two people claiming ownership of an item by having a document of sale or gift issued on the same date where Rav and Shmuel disagree - one holds it is divided and the other that it is given to the judges' discretion? How is it different from a case where a cow is traded for a donkey or a maidservant is sold and the cow/maidservant has offspring and it is unclear if the birth happened before or after the sale and the ruling is that the offspring is split between the two parties? In a case where the verdict is that the strongest one prevails, what happens if a third party comes and seizes the item? In what situations is presumptive status established immediately? Gentiles can only establish ownership with a document, not with a chazaka. Rav ruled that a Jew who claims that he/she bought property from a gentile, must prove it with a document.