Let's analyze the core differences between the plan-driven Waterfall approach and the Agile methodology.

• In Waterfall methodology, project development flows steadily downwards like a waterfall from one phase to another. The common phases are: Define, Analyze, Design, Build, Test, Launch, and Maintain. The preceding phase must be completed and signed-off before the next phase can begin. In Agile methodology, work evolves in an iterative and incremental manner with an emphasis on collaboration, responding to change, and continuous improvement. Its core foundation was laid with the Agile Manifesto for Software Development in 2001. 

• The Waterfall methodology encourages conformance to plan and processes, however, the Agile methodology values people interactions more. 

• Waterfall is the plan-driven or the traditional project management approach that requires comprehensive documentation, whereas, the agile methodology focuses on working software over comprehensive documentation.

• The plan-driven or the Waterfall approach restricts new ideas that arise during design, build, or test phases of the project, whereas the agile methodology encourages experimentation and new ideas at all times.

• Waterfall promotes a process-centric environment, whereas Agile promotes a people-centric environment.

• With Waterfall methodology, projects are dependent on contract negotiation with customers or suppliers, however, Agile encourages customer collaboration more than contracts. 

• The traditional Waterfall methodology requires conformance to a detailed project plan, whereas, the Agile methodology embraces change. The change control process in the Watefall methodoly is a very time-consuming process that requires a detailed impact analysis, a feasibility study, and possible re-distribution of resources/funds. With Agile, desired changes can simply be written as new user-stories/work items and can be added to the product backlog at any time. 

• Waterfall requires a continuous effort to motivate the team. Most often, team members are not interested in the outcome of the project. On the contrary, Agile focuses on creating high performing, self-organizing, and motivated teams. In an Agile environment, team members understand the objectives and iteration goals and feel connected to the greater purpose. 

• The Waterfall approach requires huge rework to accommodate late changes during design, build, test, or rollout phases of the project. As a result, the cost of change in this approach is quite high. On the other hand, Agile welcomes change even late in development with minimal rework, keeping the cost of change low.  

• When Waterfall is synonymous with upfront planning, Agile is all about Just-In-Time (JIT) planning. 

• With the Waterfall methodology, there's a high possibility of mismatch between approved requirements and the released product, whereas, Agile encourages frequent feedback loops that reduce any mismatch between expectations and results.

• Often, with the Waterfall approach, customers stay unhappy in spite of the effort put in by the development team. Agile methodology is customer-focused. Customers stay delighted due to frequent feedback and quick response to changes or team agility.

• Waterfall requires upfront decisions and approvals for the requirements document, the design documents, test strategy, etc. In Agile, decisions wait until the last responsible moment (LRM). LRM is a strategy of not making a premature decision but instead delaying commitment and keeping important and irreversible decisions open until the cost of not making a decision becomes greater than the cost of making a decision.

• In the Waterfall approach, there is a limited interaction between the developers and customers (especially once the design phase starts). On the contrary, Agile promotes frequent collaboration with customers with daily stand-ups, backlog refinement, iteration planning, and product demo, and retrospective ceremonies for each iteration or sprint.

More articles on Agile:

• • Agile and Lean Methodologies - Same or Different?
  • Expert Agile Tips and Techniques
  • Scrum and Kanban: Same or Different? Which one is better?
  • What are the 12 Agile Principles? Learn, Apply, and Be Agile!
  • Sample Kanban Boards - Practical Examples
  • What is a Sprint Burndown Chart? - Agile Scrum Framework

Learn more on Agile, Lean, Scrum, Kanban, and Enterprise Agility with below books:

• • The Basics Of Agile and Lean
  • The Basics Of Scrum
  • The Basics Of Kanban
  • Enterprise Agility with OKRs