The difference is that rifle bullets travel MUCH faster and tend to send a "shockwave" through the body when they hit. Depending on what they hit specifically, this can be bad or very bad for the victim.
Pistol rounds, on the other hand, pretty much just make a hole. There is a huge difference between being shot with a battle rifle and with a pistol.
Statistically, getting hit with a rifle round kills you about 50% of the time, probably renders you combat ineffective at least 75% of the time. Pistol rounds kill about 10% of the time and probably render ineffective about 30% of the time. Classic has it right.
Best wishes,
Daniel.