Grunt vs Less
No leader: the top candidate Less has only 0.21 confidence (low), below the 0.35 needed to declare a winner. The attribute-by-attribute breakdown below, with a source and date on every value, is the honest way to compare them.
What each one is
The product in its own terms, so the numbers below have context.
Grunt
A command-line tool that streamlines JavaScript development by automating common tasks such as code linting, testing, minification, and compilation through configuration files.
Less
Less is a dynamic stylesheet language that extends CSS with variables, mixins, functions, nesting, and mathematical operations, compiling to standard CSS for web projects.
Pricing
List pricing as published by each vendor, with the date we read it. Always verify at the source before you buy.
Grunt
Pricing not documented yet.
Platform & deployment
Where each product runs and how it can be hosted. A dash means undocumented, not unsupported.
Comparison generated from independently-sourced facts. Every value links to its source and retrieval date. See the method.