Why not use both DLLs? Prefer win32 wherever possible and use the lower level APIs only if absolutely necessary. Benchmark after you have figured this out. Performance is probably not a thing at this level of abstraction.
Here's one fun example from following development on Zulip: advapi.dll loads bcrypt.dll, which loads bcryptprimitives.dll. bcryptprimitives.dll runs an internal test suite every time it's loaded into any process. So if you can avoid loading advapi.dll, your process will start faster.
What makes you think they haven't benchmarked?
Here's one fun example from following development on Zulip: advapi.dll loads bcrypt.dll, which loads bcryptprimitives.dll. bcryptprimitives.dll runs an internal test suite every time it's loaded into any process. So if you can avoid loading advapi.dll, your process will start faster.