In general, a 3-way speaker sounds better than a 2-way speaker because the third speaker enhances the higher ranges of sound response. In other words, where a 2-speaker system may have low-end and high-end enhancement, relying on a central set of mid-range speakers and the car’s body for full response, a third high-end tweeter provides brighter and crisper high-range sounds than the more standard 2-speaker system. The mid-range is enhanced because not only is the car’s interior used to enhance the mid-range, but there is also a speaker in the box capable of providing the extra brightness needed at the source. The same is true of a low-end speaker, also at the source.
For more info, see 2 Way vs 3 Way Car Speakers