Updated: Jun 7, 2019
All projects have these qualities, and believe me no project is completely devoid of challenges against requirements, delivery, change requirements and goals. These intrinsic qualities of a project determine which lifecycle will be a best fit for your project.
If you have felt confused about these methodologies then this article will be of help. The easiest way to understand the fine line between these is based on two factors pre-dominantly. Namely, "Degree of Change" and "Frequency of Delivery".
Remember, planning is the only constant across life cycles. What differentiates a life cycle is not whether planning is done, but rather to what level of detail planning is done and when.
Frequency of delivery is dependent on how early you need to provide product or service updates to your customer, however degree of change drives how dynamic is your scope of requirements.
Key points which make these life cycles stand apart are:
Predictive: Take advantage of things that are known and proven. This reduced uncertainty and complexity allows teams to segment work into a sequence of predictable groupings. This is the only life cycle which needs requirement scope to be Fixed.
Iterative: Allow feedback on partially completed or unfinished work to improve and modify that work. Activities are repeated until correct.
Incremental: Provide finished deliverables that the customer may be able to use immediately. Activities are performed once for a given increment.
Agile: This life cycle leverages both the aspects of iterative and incremental characteristics. When teams use agile approaches, they iterate over the product to create finished deliverables. The team gains early feedback and provides customer visibility, confidence, and control of the product. Because the team can release earlier, the project may provide an earlier return on investment because the team delivers the highest value work first.
Thus, if you choose to implement your project using Predictive life cycles, then you will need a detailed plan which drives the work. And if you are using Agile methodologies then the team will still plan, but they will still be open to come back and re-plan as more information and details are available to the team. To make sure that they are not deviating from their intended goal a goal based roadmap shows them the way. Teams use a lot of prototyping to get early feedback of the customer. Adopting the MVP approach is also advised.