What is the difference between the Porsche Carrera trims?
 

I was looking at the Porsche website and noticed all the different Carrera trims...Carrera, Carrera S, Carrera 4, and Carrera 4S. Is the only difference between them the power (horsepower, 0-60 time, etc) or are there other differences like more luxurious/technical feautures or the body styling? Note: I call them trims but they maxisys ms908p
may technically be different cars...all Carreras though.