It seems clear enough to me which approach is the best way to develop software, but not everyone in my office seems to agree. So I thought I’d do a bit of research on the two approaches and summarize my findings here. I really wanted to find some impartial statistics that compared the productivity of the two approaches. In addition to the usual Google searches, I included information I could find from the Software Engineering Institute (SEI) and the Association for Computing Machinery (ACM).
The first comparison of the methodologies I reviewed was on pages 23-24 of a PDF I found at SEI. The comparison mapped waterfall activities to agile activities and highlighted the key difference–the waterfall methodology lacks an opportunity to demonstrate the output of an iteration and make improvements based on feedback.
The first statistics I could find came from this wiki entry. While they’re specific to a single company, they make a very compelling case for the use of agile methods. Agile methods (specifically SCRUM) delivers more lines of codes, with fewer defects, in less time than waterfall methods.