The short answer
Build the full product first only if it is genuinely unusable in a smaller form. In every other case the smaller version answers the expensive question, which is whether anyone wants it, for a fraction of the money.
The comparison
| MVP first | Full build first | |
|---|---|---|
| Cost | £2,999 to £5,999 | £20,000 to £60,000+ |
| Time to real users | 14 days | 3 to 6 months |
| What you learn | Whether people want it | Whether you can build it |
| Cost of being wrong | Two weeks and a few thousand | Months and most of the budget |
| Risk of feeling incomplete | Real | Lower |
| Risk of building the wrong thing | Low | High |
The last two rows are the trade. You are choosing which risk to carry.
The three cases for building the full thing
1. It genuinely does not work smaller. Some products need two sides transacting from day one. Test that assumption hard, though: plenty of marketplaces launched by doing one side manually.
2. Compliance gates the launch. If you cannot legally operate without a full feature set, there is no smaller version to ship.
3. Funding is tied to a specification. If an investor or funder has agreed a scope, that is a commitment, not a product decision.
The case against, in one paragraph
Common questions
Is an MVP always the right first step?
Not always. If your product is unusable without two sides transacting, if compliance gates the launch, or if you have funding tied to an agreed feature set, build the fuller thing.
Won't a small launch damage our brand?
A small product done well does not. A big product done badly does. The risk people worry about is being incomplete; the risk that actually materialises is being mediocre across too many features.
How do I know when to build the rest?
When real users tell you, through what they do rather than what they say. That is the entire return on launching small, and it is why the version-two list is more valuable after launch than before.