HMMMM?
A close-up shot of 45 Long Colt ammo on the left and 45 ACP ammo on the right.
John Browning didn't set out to create an entirely different cartridge than that which the U.S. Army had become accustomed to. He actually developed the 45 ACP to match the ballistics of the 45 Long Colt fairly closely! It's not an apples to apples comparison, though. A typical 45 Long Colt cartridge has a 250 grain bullet and 860 fps muzzle velocity, giving it 411 ft lbs muzzle energy.
In comparison, a standard 45 ACP cartridge has a 230 grain bullet and 850 fps muzzle velocity, giving it 369 ft lbs muzzle energy. The 45 Long Colt is effectively a more powerful cartridge, but with a 1911 you get seven shots in the magazine instead of six in the cylinder. It's a lot easier to reload a semi-auto than a revolver when you're in a hurry, too, which is why they're generally more favored. The 45 Long Colt has a .452" bullet.
The 45 ACP, on the other hand, has a .451" bullet. If you consider one one-thousandth of an inch a great length, then you may argue that the two cartridges' bullets are in fact very different from one another. It's going to be a tough sell, though.