It's like asking what are the differences between Visual Studio and Notepad++. Literally >90% of the tools in Excel don't exist in Calc. And there are big ones in the list (eg. pivot table, vba macros, solver), not just small feature..

A very basic example, Calc doesn't have tables. That's enough for me to not want to use it, but there are probably a dozen of those for me.

I mean this literally: Everything you can do in Calc, Excel is better at in either UX or performance, usually both. Even typing formulas in cells is snappier in Excel.