We could go into a lot of detail about the benefits (and some drawbacks) of brushless motors, like the kind you'd find in Milwaukee FUEL lineup, but this Youtube video does a great job at explaining it in a lot of great detail.

One huge benefit of this Milwaukee impact driver is the size. This thing is compact and powerful, making it easy to fit into most work spaces. Reviews always mention that it feels like a 20V motor packed into a 12V tool.

It's currently 40% off on Amazon — a significant discount off other stores.