Both are true, though, if you consider a non-power-user's perspective. Calc is behind Excel and Sheets in usability, but ahed of Sheets (and behind Excel) in "power". You can do more with Calc out of the box, but it's much more annoying to use than Sheets and if you don't need that power, Sheets is the better choice (ignoring philosophical issues).

I would agree that "Calc" has worse usability if you're talking about OpenOffice. I find LibreOffice's Calc to be as usable as Excel because it reminds me of Excel 2003 (and older). Additional anecdata: I asked my wife who hates using Excel and she said that LibreOffice Calc was no different.