Vanilla JS is easier for me. I don't have time to learn the workings of coffeescript just to read a library casually.
There really is very little magic with coffeescript. Most of it is syntactic sugar which can be learned at a glance of: http://coffeescript.org/ .
Don't mean to come off as pushy but I think it's well worth learning what coffeescript is. Especially if you are familiar with javascript, as it's a straight upgrade in your toolkit.