How can we reconcile the benefit the two Sahihs provide for theoretical knowledge with the discarding of one of them due to a preponderant argument when there is a contradiction?

The two Sahih collections (Bukhari and Muslim) have been accepted by the Ummah, so all their narrated hadiths are considered authentic by scholars. Accepted hadiths, if free from contradiction, are definitive and must be acted upon. If two hadiths contradict each other, then either they are reconciled, or it is determined which of them abrogates the other, or recourse is made to preference if the abrogating from the abrogated is not known, and the preferred one is acted upon. This does not diminish the status of the Sahih, rather it prioritizes the more preponderant hadith.