fast builds isn't the entire broccoli offering, I would trade slow builds for accurate consistent and durable builds, amazingly with broccoli I get both.
I actually do not believe grunt/gulp vs broccoli makes terribly much sense to compare as broccoli aims to be a accurate/stable/fast build pipeline, it does not aim to replace your task runner. It's primary goal is to be the best possible build pipeline, and should be programmatically accessible to your existing task runner.
Anyways, since I didn't really compare grunt/gulp with broccoli, let me explain what you get:
* primitives make sense, was able to get a fairly non-trivial or ordinary pipeline setup really quickly
* builds so fast, you don't notice them.
* accurately handles changes (deletions and git branch changes tend to often cause similar tools issues)
* doesn't lose changes that occur while building
* true pipeline. eg. describe the transforms, and the system handles the rest. No needing to construct make-shift pipelines yourself
* immediately usable as server (error reporting, locking)
* development builds.
* minified source mapped production builds.
* the Broccolifile API is well suited for constructing custom piplines
And finally:
the above you essentially get for free, if you need customizations the Broccoli file provides are an API well suited for the task.
