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It depends how you're using it. If you have a bunch of data you're just wanting to upload and reference, then Excel/CSV files is fine. If you want people to be actively editing the files and want more control over how they input the data and what they can do to your source, then SP lists are better. You can give users contribute access to the list, where they can edit/add data but not modify the list structure (which you want, because people modifying the list structure will often break things).