Doing so will make it harder (but not impossible) for outsiders to access the folder; however, it also means everyone you share the folder with must have a Microsoft account. If you leave the second setting as-is (with no Microsoft account required), anyone you share the folder with can then forward the link to others via email. Those people — who you may or may not know — will easily be able to access and edit the folder. Whether that's a pro or con depends on your perspective and needs.
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