A variety of life cycle models for software systems development are generally available. However, it is generally difficult to compare and contrast the methods and very little literature is available to guide developers and managers in making choices. Moreover in order to make informed decisions developers require access to real data that compares the different models and the results associated with the adoption of each model. This paper describes an experiment in which fifteen software teams developed comparable software products using four different development approaches (V-model, incremental, evolutionary and extreme programming). Extensive measurements were taken to assess the time, quality, size, and development efficiency of each product. The paper presents the experimental data collected and the conclusions related to the choice of method, its impact on the project and the quality of the results as well as the general implications to the practice of systems engineering project management.