Hi zosea,
Thank you for your stress test result. The reason that HSSFWorkbook is much faster than XSSFWorkbook is because the internal implement of xls and xlsx. xls is using binary to save data but xlsx uses xml. Binary serialization is always fast enough but xml serialization doesn't. Moreover, we do find that there is big performance issue with XmlSerializer. That's why it looks so slow.
Thank you for your stress test result. The reason that HSSFWorkbook is much faster than XSSFWorkbook is because the internal implement of xls and xlsx. xls is using binary to save data but xlsx uses xml. Binary serialization is always fast enough but xml serialization doesn't. Moreover, we do find that there is big performance issue with XmlSerializer. That's why it looks so slow.
