Other than cosmetics, the only difference is the guide rod. The protector has a full length guide rod, the CQB does not. You will get many different opinions about the use of a guide rod. At the end of the day, I went with the Protector. I like the all black finish. Either way you won't go wrong. If you go with the CQB and later decide you want a full length guide rod, you can always drop one in. The difference between the 2 is only $50.
I talked a lot with Terry Peters. He shoots straight and will help you pick the gun that is right for you. Give him a call. He helped me a lot. He comes highly recommended by others as well.