Custom software vs SaaS isn't a matter of personal preference — it's a decision that will shape how a company operates for years to come. An off-the-shelf SaaS solution brings a quick start and a lower entry barrier, while custom software offers an exact fit with processes and full control over data and future development. The right choice doesn't depend on what a competitor used or what a vendor recommended at the first meeting — it comes down to a combination of six criteria that need to be assessed systematically.
Custom Software vs SaaS: What Are We Actually Comparing
When a company weighs custom software vs SaaS, it's actually comparing two different operating models, not just two ways of building software. An off-the-shelf SaaS solution is a standardised product leased by many companies at once — its features, design, and infrastructure are shared, and the vendor decides on changes according to its own development roadmap. Custom software, by contrast, is built specifically for one company's processes, and that company chooses the scope of features, the way it integrates with other systems, and the pace of future development.
So the difference isn't just in how the solution is built, but in who stays in control of it once processes, data volumes, or regulatory requirements change a few years down the line. That's the basis for the decision framework below.
Six Criteria That Decide
No single criterion decides on its own — what matters is the combination of all six in relation to a specific company and its processes.
| Criterion | When it favours SaaS | When it favours custom software |
|---|---|---|
| Process fit | The process is standard and similar across the industry | The process is unique or a source of competitive advantage |
| Scalability | User numbers and demand fluctuate frequently | Growth has a specific character that standard tools don't cover |
| Integrations | A connection via common, public APIs is enough | Deep integration with internal or legacy systems is required |
| Security and data | Shared infrastructure meets the company's requirements | Strict regulation or specific data requirements apply |
| Ownership and independence | The company accepts dependence on the vendor's roadmap | The company wants control over the pace and direction of development |
| Long-term maintenance | The company doesn't want to handle its own operations and updates | The company has the capacity and interest to develop the solution long-term |
Process Fit Matters Most
If a company can adapt its processes to how a standard SaaS tool works without major compromises, that's a strong argument for an off-the-shelf solution — deployment is simpler and the company doesn't depend on its own development team. If the processes are unique, or if they're exactly where the company builds its competitive advantage, adapting the company to the software usually creates more friction than benefit.
Integrations and Security Change the Equation
Companies with an extensive environment of existing systems — ERP, internal databases, specific APIs — often find that a SaaS tool requires workarounds or extra connectors that complicate maintenance. Similarly, in regulated industries such as finance or property management, requirements around data location, auditing, or access rights can be easier to meet with dedicated software than within a multi-tenant SaaS architecture.
The chart below illustrates the general principle: as the need for customisation grows, so does the level of control a company needs over the solution.
When an Off-the-Shelf SaaS Solution Pays Off
- The process is standard and similar across the industry — for example invoicing, emailing, or project management.
- The company needs to get the solution up and running without its own development team and without long-term responsibility for maintaining it.
- User numbers and demand fluctuate, and flexibility in subscription scope matters more than depth of customisation.
- It isn't an area where the company builds its competitive advantage.
When Custom Software Pays Off
- The processes are specific, and no off-the-shelf tool covers them without major compromises.
- The company needs deep integration with internal or legacy systems — in that case, it makes sense to assess the options for custom development from the very start.
- The solution is meant to be part of a product the company offers its own customers — as shown, for example, by the platform for financial services, custom software can also work as a standalone product, not just an internal tool.
- The company plans to develop the solution long-term and doesn't want to be dependent on an external SaaS vendor's roadmap.
Hybrid Approach: SaaS and Custom Software Together
The choice doesn't have to be all-or-nothing. A common practice is to keep standard functions — accounting, HR, email — in off-the-shelf SaaS tools, and deploy custom software only where the company needs to be different: in its own automation, in system integration, or in processes that directly generate value for the customer. The approach to assessing which processes are worth prioritising is covered in the article on business process automation — the same logic applies when deciding between SaaS and custom software.
How to Decide
A six-criteria decision framework gives a company a shared language for the discussion, but the specific weight of each criterion varies from project to project — it depends on the mix of processes, existing systems, and where the company plans to grow. That's why it makes sense to assess the situation with someone who understands both sides — deploying SaaS tools and building custom software — and who can recommend a solution without being biased towards either one from the start. If you're not sure which direction makes sense in your situation, you can discuss your specific processes via a no-obligation consultation.