Building your own team buys you the most control. The people absorb the business domain over time, and this context remains inside the company. The price comes in the form of slow hiring and fixed overhead: recruiting a strong engineer is slow, onboarding adds more time, and the cost keeps running through the quiet quarters.
Project outsourcing is the arrangement where the vendor owns delivery: the provider staffs the project, the partner manages the day-to-day work, and the provider carries the staffing risk. This fits well when the outcome can be described and you have an available product owner. It breaks down when the requirements change weekly, since an external team cannot invent your business rules.
Team extension is the middle option: you add engineers but keep the planning and the management on your side. It moves quickly — a matching profile can join almost immediately — and it winds down as quickly as it ramped up. The trade-off is that your engineering managers have to have time for code review and planning. If that capacity is missing, you end up paying hourly for uncoordinated work.
In practice, companies blend them. One durable pattern puts the architecture and the core domain with permanent staff, while an outside vendor covers peaks, well-defined modules or platform work. The line holds: hold on to the parts that are hard to re-learn, difference between livewire and alpine js contract out what is well understood.
Three simple questions resolve most of these debates. To begin with: is this software central to how you make money, or a cost centre? Second: over what horizon will you need this capacity — one project or a permanent roadmap? Finally: who answers the phone at two in the morning when it breaks? Answer those honestly and better than php the right arrangement is normally clear.