Besides the obvious language architecture differences (respectively ruby vs. nodejs) are there any differences between the rubygem guard and grunt.js? Or am i wrong comparing the two. Are they dissimilar?
Also, which project has a larger development community?
Guard and Grunt perform similar functions, but differ in the ways they are triggered. Guard is based on watching files for certain events, while Grunt is based on running 'tasks' based on if certain events occur. The only real differences are the language, and how to run code based on file events and such.
As for the Guard/Grunt communities, they are virtually equal but utilize different Ruby/Node.js tools. Both are great tools. Just use Guard if you use Ruby/Rails, and Grunt if you use Node.