Building your own team buys you the most control. The engineers absorb your domain over months and years, and that knowledge sits in the building. The cost comes in the form of slow hiring and fixed overhead: hiring well is slow, cross platform app development company ramping up takes several more weeks, and symfony ecommerce framework the cost keeps running whether the roadmap is full or empty.
Full outsourcing implies someone else is accountable for shipping: they staff the team, the provider manages the day-to-day work, and they absorb the risk of missing the date. This works well when the work is a defined project and you have someone who can make decisions quickly. It breaks down when the requirements change weekly, because a vendor cannot guess what the business wants.
Staff augmentation sits between the two: you add engineers but keep responsibility for delivery in-house. It moves quickly — the right specialist is often available in weeks rather than months — and it winds down as quickly as it ramped up. The catch remains that your technical leaders need time for code review and planning. If that capacity is missing, you end up paying hourly for uncoordinated work.
Most of the time, the models mix. A common pattern puts the architecture and the core domain in-house, while a partner handles discrete features, migrations or mobile clients. The line is simple enough: keep the parts that are hard to re-learn, and outsource what is well understood.
Three simple questions usually settle it. To begin with: is this software the product itself, or a cost centre? Then: over what horizon will you need this capacity — months or years? Last: who answers the phone at two in the morning when it breaks? Answer these three honestly and the model is normally clear.