The farther and slower you are shooting the more bc makes a diff. As
@dougduey said higher vel from lighter bullets will overcome to a point. Higher bc bullets will always take over for wind and drop at some point down range. Often this is farther down range than is needed. The 20% lower density in material between copper and lead, makes it impossible for a copper bullet to achieve the same bc as a lead bullet. Can't beat physics.
If you compare the physical size of our 143g Hammer Hunter to a 160g AB they are roughly the same size. As was mentioned our bullet is going to retain 70% of its weight whether it impacts at high or low vel. The physical size of the projectile plays a role on impact and after deformation. The lighter 143g bullet will wind up being physically larger than the heavier lead bullet after impact. Then comes the most underrated factor in the choice of hunting bullets. Impact Velocity. Speed kills. The shock that is imparted on the animal from a high speed impact than is shedding 30% of it's weight as quickly as possible is simply impressive. Then having a retained shank that is flat on the frontal area that will straight line penetrate regardless of bone or not, creates a large initial wound channel that then continues a nice wound channel all the way through the animal. The more permanant wound the quicker the kill. This is, and always will be the most important to aspect to our hunting bullets.
Roy Weatherby and others were ahead of their time knowing that impact vel on animals is priceless. There just were not many bullets that could hold up to the launch speeds or the impacts at high vel. We don't have issues with either.
Good luck in your quest and good hunting.