Two models account for most outsourcing arrangements. In a dedicated team, the provider supplies named people who work for you, and you direct the work. In a managed process, the provider takes responsibility for an outcome against a service level, and decides how to staff it.
The choice is less about size and more about how well the work is defined.
Choose a dedicated team when
The work changes frequently, depends on context, or benefits from the same people learning your business over time. Bookkeeping and month-end, customer support, executive support and technical help desks tend to fall here. You want to talk to your team, not to a service manager.
Choose a managed process when
The work has clear inputs, outputs and quality criteria, and you would rather measure results than manage people. Data entry, document data extraction, order processing and ticket queues often fit. Volume can vary and you want capacity to be the provider's problem.
Watch for the mismatch
A dedicated team for well-defined, volume-driven work means you are paying for management you do not need. A managed process for work that is still being figured out means service levels get argued about instead of met. Many engagements start as a dedicated team and move to a managed process once the work is documented and stable, which is a healthy direction to travel.