Sorry, but KE = 0.5 × m × v^2 Kenetic Energy = Mass * Velocity squared. Velocity wins. For stopping power?
"The kinetic energy of an object is equal to the work, or force (F) in the direction of motion times its displacement (s), needed to accelerate the object from rest to its given speed."
Kinetic Energy So it requires more kinetic energy to accelerate a larger mass. Thus, it requires more energy to get an 18 wheeler to go 55 MPH than a motorcycle, but once it reaches that velocity it acquires more force if it collides with another object than the motorcycle. If the 18 wheeler collides with another object at 55 MPH it will do far more damage than the motorcycle. It's the same with the bullets. The larger mass bullet travelling at the same velocity as a lesser mass bullet will hit with more force and do more damage to the target. It's just physics.
Yes no and maybe.
Comparing firearm projectiles to vehicles makes no sense.
Two different means of injury.
A bigger bullet doesn’t always mean more injury. Bullet design has a lot to do with it.