docx/xlsx are better, they are zipped XMLs too, just like odf. Older ones, doc & xls are closer to sqlite, for the same reason, performance. I remember finding

docx/xlsx are better, they are zipped XMLs too, just like odf. Older ones, doc & xls are closer to sqlite, for the same reason, performance. I remember finding confidential information in these files received from third parties they probably didn’t want to disclose, e.g. offer price that was before the last edit.