Here are a few pros and cons of using a keyboard and mouse configuration compared to the Xbox360 Controller.
Pros:
-Hipfiring, Target Tracking, and Turning are easier.
-Recoil Compensation is much better.
-Ability to use Macros.
Cons:
-Might not be good for controlling vehicles that are ment to be controlled using an xbox controller
-Some games might not work well with the two device configuration.
Honestly i prefer the mouse and keyboard over the controller.