Fixed price Model:
Pre-defined Project scope and Requirements.
Changes to scope will require re-estimation of cost and delivery dates.
Fixed Project cost and duration.
Useful for small and medium size projects with clear and defined requirements, well established software development practices and time line where there is very little change.
Time and Materials Model:
Cost based on the Resources and the experience of the Resources.
Billing based on amount of work provided in the Billing period.
Dedicated and flexible team model available.
Useful for projects with a high level product plan but Requirements are not clear in the beginning of the Project.