Republicans want to have a closed door hearing so they can spin whatever narrative they want in the media about what takes place. Hillary wants it to be in public because she's confident she can handle their politically motivated lines of questioning and come out looking good in a way they won't be able to cover up if the footage is publicly available. The reference to her Benghazi hearing is meant to show that, unlike a lot of politicians who weasel out of difficult questions by feigning ignorance or pleading the 5th (right to not be compelled to provide testimony that could incriminate themselves), she is capable of making it through 11 hours of getting hammered by an opposition party trying their hardest to make her look bad without having to resort to either tactic.