An in-house team gives you long-term retention of knowledge. The developers absorb the business domain over time, and that accumulated context sits with you. The catch shows up as time and rigidity: filling a senior role is slow, ramping up adds several more weeks, and the cost continues whether the roadmap is full or empty.
Project outsourcing implies someone else is accountable for shipping: they staff the project, the partner manages the plan, and the provider carries the delivery risk. This works well when the scope is reasonably clear and your side has someone who can make decisions quickly. It works badly when nobody on your side owns the product, as an external team cannot invent your business rules.
Staff augmentation sits between the two: you bring in developers while keeping the management yourself. It moves quickly — the right specialist can join almost immediately — and it scales down as easily as it scales up. The condition remains that your technical leaders must have the bandwidth to manage them. If that capacity is missing, you are paying hourly for uncoordinated work.
In the real world, companies blend them. A common pattern puts the architecture and symfony vs spring boot comparison the core domain inside the company, while a partner handles discrete features, migrations or mobile clients. The rule is simple enough: retain the parts that are hard to re-learn, and outsource anything a competent team can specify and deliver.
A few questions generally decide the matter. Start here: is this enterprise software development company a core competitive asset, or internal plumbing? Then: over what horizon will the work last — a quarter or a decade? Third: who answers the phone at two in the morning when it breaks? Answer these three honestly and the right arrangement usually chooses itself.