What is the difference between Less and Sass?

The difference between Less and Sass are :

Less :
* It uses JavaScript and client-side.
* It is processed at client side.
* It uses @symbol to declare variable.
* It doesn’t inherit multiple selectors.
* It doesn’t work with unknown units.

Sass :
* It uses ruby and processed at server-side.
* It is processed at server side.
* It uses $symbol to declare variable.
* It inherits multiple selectors.
* It allows us to work with unknown units.