The Surefire G2X Pro and G2X Tactical are virtually the same as the 6PX series. The only difference between the two is the body. The G2X series has a plastic body referred to as Nitrolon, while the 6PX models have an aluminum body. Price is also adjusted accordingly, making the G2X models a bit cheaper than the aluminum.
Max brightness and mode of operation is the same between the two series. The pro model has two brightnesses, while the tactical has only one. Both models still utilize 2 CR123 primary batteries. These are perfect for use as weapon lights, or even a defensive tool. The tightly focused beam makes it easy to light up the desired spot, directing all 200 lumens into one small area.
The choice between the Nitrolon and aluminum models may be tough, but take solace in the fact that whichever light you choose is going to be great.