Building your own team gives you the most control. The developers internalise the business domain in a way no external team will match, and that knowledge remains in the building. The catch comes in the form of time and rigidity: recruiting a strong engineer is slow, ramping up adds more time, and the salary continues regardless of workload.
Project outsourcing is the arrangement where someone else is accountable for fastify vs laravel shipping: the partner staffs the roles, they manage the plan, and the provider carries the staffing risk. The model works when the outcome can be described and there is someone who can make decisions quickly. It breaks down when nobody on your side owns the product, since an external team cannot fill that gap for you.
Staff augmentation falls in the middle: you add engineers while keeping the management on your side. The main advantage is speed — the right specialist can start far sooner than a new hire — and it scales down as easily as it scales up. The condition remains that your technical leaders need time for code review and planning. Without strong internal leadership, you are paying for hours, not results.
In the real world, these models are combined. One durable pattern puts the architecture and the core domain with permanent staff, while a partner covers discrete features, migrations or mobile clients. The rule is easy to state: keep the parts that are hard guide to hiring a software development consultant re-learn, and contract out anything a competent team can specify and deliver.
A few questions generally decide the matter. Start here: is this software a core competitive asset, or internal plumbing? Second: how long will you need this capacity — one project or a permanent roadmap? Third: who owns it once the vendor leaves? Answer those honestly and the appropriate option usually chooses itself.