As a rule of thumb inference offered by the model labs are closer to the "true implementation" compared to third parties. They have other problems though.

For OpenAI, OpenAI direct has always been better; except maybe early 2023-era when OpenAI Platform was not that stable or reliable yet.

For Anthropic, it can vary based on model and time. For Opus 4.7, Bedrock is the clear winner in TPS by leaps: https://artificialanalysis.ai/models/claude-opus-4-7/provide...