It would be hectic for the company to go forward with implementing the new system through phase implementation plan. The implementation by phase approach is rather time consuming. Introduction of the integration system in phases shall end up consuming a lot of time before the company can realize the objective of eliminating the legacy systems. The workers too will not be zealous enough. It is especially so because they have enough time to learn working with the integrated system. Conversely, the parallel system is no better. Here, the workers too will not work hard enough. They shall find it easier, more often than not, to work with the legacy system. This shall lead to NIBCO taking more time than planned to phase out the old system. Also, the two methods are more expensive to implement in comparison with the big bang approach.
Vaidyanathan Ganesh. Project management: process, technology and practice. U.S.A:Pearson Higher Education.