Though two-point seat belts (a belt without a chest strap, having only two points of attachment at each hip) exist, they are much less common in cars. They are typically found in buses, planes and other mass transit. Three-point seat belts, with both a lap and shoulder belt, are what you will find in most vehicles. They are considered much more effective, as the three point belts spread the force across more of the body. This minimizes the strength of the force in one area and, by default, injury.
It is important to remember that seat belts are designed for adult bodies. Car seats, then, are a must as they safely disperse the force of the stop in an accident.
Seat belted passengers are always considered to be safer than unrestrained ones, as according to the NHTSA, “During a vehicle crash, being buckled up helps keep you safe and secure inside your vehicle, whereas being completely thrown out of a vehicle is almost always deadly.” Safety is always top priority – a car can be repaired, but injuries are harder to recover from.