An impact driver is relatively new on the home improvement scene. It is essentially an electric drill with an electric hammer component. Due to this impact driver is better and more adept at drilling in screws. Also the impact driver has more torque than a standard electric drill and can screw in screws with a standard electric drill cannot.

However, this additional power comes an a price. The impact driver is typically more expensive than a traditional electric drill and it also more difficult to use.

In my experience, unless you are drilling into a lot of dense material, than a standard electric drill is all you need.

I have never needed any more power than was already found in my Hitachi 18 volt lithium drill.

This drill can be found on Amazon here, and a picture is below: Hitachi DS18DBFL2S 18V Cordless Lithium Ion Brushless High Torque Driver Drill (Includes One 3.0Ah Compact Battery)