Core answer
Start here. This is the direct spoken answer to practice first.
Overview
The shortest API path and the best organizational operating model are not always the same choice.
A direct model API can offer the newest provider features and a simpler relationship when one application and one provider are enough. A managed cloud platform can integrate models with the organization's identity, private networking, billing, policy, regional controls, and adjacent AI services. I choose from workload requirements and operating constraints, not from the number of models advertised.