Difference Mercedes s class 430 and 500?

Like many car companies, mercedes tends to name its cars after their engine sizes. Though not accurate on some models, that tendency applies here. The S430 has a 4.3 liter V8 engine while the S500 has a 5.0 Liter v8. So essentially, if you care about fuel economy more than horsepower and torque, you would want the smaller engined car, the s430. However, if you only care about power, you would want the s500. Though, if you are in the market for such a car, I would recommend the s63 amg.