Fixed price, time-and-materials, dedicated team — the choice of delivery model is often treated as an administrative detail. It is not. The model decides who bears the cost of uncertainty, and uncertainty is the defining feature of software. Choosing well begins with an honest read of how well-defined your requirement actually is.
Fixed price
Fixed price feels safest to a buyer: one number, one deliverable. It works well only when scope is genuinely well-defined and stable. When it isn't, the vendor prices in a risk premium, guards scope tightly, and recovers any surprises through change requests. Paradoxically, fixed price on a vague requirement can become the most expensive and adversarial model of all — every clarification becomes a negotiation.
Time and materials
Time-and-materials shifts flexibility to you and risk onto your budget. It suits genuinely exploratory work where requirements will evolve. Its danger is the absence of a ceiling: without independent oversight of hours and progress, spend can drift with little to show for it. It rewards buyers who govern actively and punishes those who don't.
Dedicated team
A dedicated team gives you sustained capacity and continuity, effectively renting a stable group over time. It fits ongoing product development more than one-off builds. Value depends entirely on the seniority and stability of the people assigned — and on your ability to direct them well, which usually means having someone technical on your side.
How to choose
- Well-defined, one-off scope with little expected change → fixed price, with tight acceptance criteria.
- Exploratory or evolving scope → time-and-materials, with independent governance of hours and progress.
- Ongoing product with a long horizon → dedicated team, with attention to who is actually on it.
There is no safest model — only the model whose risks match your situation. The specification decides which one that is.