Approval software should fit the rules governing a decision. The visible approval button is only a small part of that fit.
Evaluate a purchased tool with exceptions
Prepare cases for a revised submission, an absent approver and a rejected item that returns for review. Check whether the tool preserves the relevant history and makes the pending decision clear.
Ask what configuration covers these cases and what requires an external workaround. Include setup, migration and ongoing administration when comparing options.
Identify a reason to build
Custom development becomes a candidate when important rules cannot be represented reliably in the evaluated tools. This may involve role-specific visibility, dependencies between decisions or a particular integration.
Document those mismatches precisely. Disliking a default screen is a different problem from being unable to enforce a decision rule.
Compare ownership after launch
Buying introduces dependence on a vendor's model and changes. Building requires maintenance, support and a responsible owner. Compare both against the effort and consequences of the current process.
A workflow assessment can start with the cases rather than a preferred solution. If email still handles the task adequately, the email vs task-system comparison helps identify when that changes.