It's been maybe 4 years since I last tried LibreOffice, but at the time, the calculation speed in Calc was *much* slower than Excel's once workbooks got to an even moderate size and formula complexity. Working in financial systems, I can say that LibreOffice would have been completely, 100% unworkable at our company (with people wasting tremendous time waiting for workbooks to calculate). The situation may well have changed since I last checked, but unfortunately (very unfortunately considering how expensive Office is) at the time LibreOffice wasn't even an alternative for finance-focused work.