ERP vs PSA
ERP and PSA solve the same problem, one shared set of records, for different kinds of business. ERP is organized around goods, stock and financial processes. PSA is organized around billable time: quoting effort, staffing it, recording it and invoicing it.
What does PSA do that ERP does not?
It treats the quoted effort, the recorded hour and the invoice as one chain. From that come utilization, billability and project margin, which classic ERP does not produce because it was never built to ask those questions. PSA is organized around billable time: quoting effort, staffing it, recording it and invoicing it.
What does ERP do that PSA does not?
Materials, stock, procurement, production planning and the depth of financial accounting that comes with them. A business manufacturing physical goods needs those, and will not find them in a pure PSA system. ERP is organized around goods, stock and financial processes, while PSA is organized around billable time.
Can one system do both?
Yes, and several do. The question to ask a vendor is not whether both words appear in the brochure, but whether a billable hour and a quoted effort are first-class objects in the system or something attached to a materials model.
Which one does a project business need?
If the unit sold is an hour or a day, the PSA capability is what decides whether the business is profitable. Whether it arrives as a PSA system, an ERP with project modules, or one system covering both is a question of fit rather than of category.
troi covers both sides for project-based companies. See all features.