Vendor-Supplied ROI
Pros: Easy and inexpensive method to justify IT purchases.
Cons: Figures are "averaged" and may not reflect returns for an organization like yours; positive returns often inflated.
Internally Generated ROI
Pros: Forces you to justify IT purchases with hard numbers tailored to your type of business; forces IT and business units to collaborate; bridges communication gap with financial management.
Cons: Organizational pressure and lack of business expertise often produce unrealistic numbers; analysis is performed early in the life of a project, when little is known about returns; numbers are seldom revisited after project goes live; difficult to apply to knowledge-based businesses.
Investment-Portfolio ROI
Pros: Encourages periodic re-examination of assumptions and results; rewards experimentation; requires collaboration among IT, finance and business units, fostering accountability.
Cons: Can become burdensome if reviews occur too often; still difficult to apply to knowledge-based businesses.