Coming straight to the point, Tesla Model S is a premium sedan, flagship with improved acceleration, displays & customization options while Tesla Model 3 is developed as a mass market and really economical vehicle. Also, it is true that model 3 is the newest model in the market however, it is to be noted that model 3 is not the version 3 or the latest model. Similar to model S, it is undoubtedly the safest car in the class. But, both Tesla S and 3 are leading cars built on the 4th version of Tesla technology.