This agrument is as old as firearms. Military firearms have went down in caliber since the military first started useing firearms. There does come a point at which liter bullets leaveing the gun faster becomes a loseing propisition. As the bullets get liter their ballistic coefficient get lower, which means they drop velocity at a faster rate. There does come a point at which the maximum range will decrease because the BC of the bullet ( which is basically a measure of it ablity to retain velocity) get so low the the heaver bullet with the higher BC will travel farther.
There is one other big consern about high velocity lite bullets versus heavy slower bullets and their effect on game. While a lite fast bullet will have more kenitic energy that does not mean it will be more effective at stopping or killing game, especially dangerious game. Lite fast bullets will eather blow and not penitrate on heavy skinned game, or it will punch a very small hole and not deliver it`s energy effectively. There was an Aferican guide named Taylor that said Kenitic Energy was a usually was to figure the effective stopping power of a round on dangerious game. He preposed his own knock down formula, The Taylor Knock Down Formula. It says velocity X bullet weight X diameter of the bullet. Is a far better way to figure the effectiveness of a round than 1/2 MV2. As a matter of fact most afferican guides do not want a round for dangeriuos game that has a muzzle velocity of over 2,400 fps. They prefer the largest diameter and heavest bullet that they can stand to push at 2,000 to 2,400 fps. saying it is the most effective at stopping dangerious game.
If you hunting deer in this country stopping it is not the question as most people have far more gun than needed any way, it becomes a question of how much meat do you want to destroy.