G7 BC is better than G1 BC because it provides a fairer comparison between different bullets and more resembles the modern high velocity long range rifle bullet. Consider a bullet from two different manufacturers. It’s possible for them to have different advertised G1 BCs if the BCs are calculated for different velocities. G7 BC would be the same, even at different velocities.

 

image of ballistic performance and variation of .243 caliber 105 grain target hybrid