* Chevrolet Malibu: This is a specific model of car, a mid-size sedan. It's a distinct vehicle with its own design, features, and available engine options.
* Chevrolet LS: This refers to a family of small-block V8 engines produced by Chevrolet. It's not a car model itself, but rather a powerplant that has been used in many different Chevrolet vehicles over the years (Camaros, Corvettes, trucks, etc.). Think of it as a type of engine, not a type of car.
In short, you wouldn't compare a Malibu to an LS like you wouldn't compare an apple to an apple seed. A Malibu *might* have an LS engine *in it*, but the LS is a component, not a complete vehicle.
