In a game, a machine gun is more fun. In real life, the sniper rifle is more effectice as it costs a lot less and has more of a psychological effect on the enemy. There was a time where a rebel group in the mountains would use snipers to pick off the first man in government patrols. Eventually, no one wanted to be the first man and the patrols stopped. But, in Vietnam, Charlos Hathcock apparently used an M2 .50 caliber machine gun as a sniper rifle with an attached scope, so the best of both worlds I guess with that.