Low carb option has more total protein than the double protein. With only 3 calorie containing nutrients (fat/protein/carb) cutting one of the three down is bound to result in an increase in the other two to meet calorie needs.
That being said, protein isn't the only option for gaining weight and bulking up. For bodybuilding the double protein would actually suit you best as carbohydrates trigger stronger insulin release and insulin post-exercise allows the energy from carbohydrates into the muscle (leading to growth).
If you're living a pretty sedentary lifestyle, the same insulin release will allow that energy into fat cells instead which is why lower carb diets are sometimes helpful for less active people.