When SaaS usually wins
A market solution is a good candidate when the process is common, configuration covers the main needs and integration does not create a critical dependency.
Buying also transfers part of maintenance, operational security and product evolution to the vendor. For a small business with no technical team, that value weighs heavily in the comparison.
When building makes sense
Custom software gains weight when the workflow is genuinely specific, integrates proprietary systems or data, needs control a SaaS product cannot offer or embodies a differentiating capability.
It can also make sense when fragmented tools force the team to copy information or reconcile states, or when per-user subscriptions grow without adding value.
The middle option: integrate
The decision is rarely binary. Many effective architectures retain standard products for common capabilities and build a proprietary layer to coordinate data, permissions and experience.
For an SME, this is often the prudent path: keep what works, connect what is loose and build only what differentiates.
Compare total cost
Compare licences, implementation, customisation, integration, migration, vendor dependency, maintenance and switching cost. Include training, errors, manual controls and time lost between systems.
A decision that can be revisited
Define what would need to be true to buy, integrate or build. Validate the main risk first: the need, integration, performance or adoption.
What is bought today can be built tomorrow and vice versa. Decide for the next twelve months, not forever.