The advantage of Gulp, in my opinion, is that it's driven by code rather than config - that is to say, in order to define your tasks you write JS code instead of JSON. That gives you a considerable advantage in cases where you want to do something outside of the scope of what the plugin developer was thinking.

Of course, that brings with it the disadvantage of needing to be able to write JS in order to configure it, and an additional point of failure (eg your own code).