My company soured on Marshmallow a while back due to performance. Maybe it’s gotten a lot better, but it has a bad reputation here. Most people seem really happy after we started using Pydantic. Take all that with a grain of salt since I’m just parroting hearsay :)
Personal opinion: pydantic crushes Marshmallow. Not even a fair fight. Pydantic is more performant, has better mypy/linter integration, and more powerful data model. We had a project where we pre-emptively used marshmallow to marshall/validate data. Had to remove that and solely use it at the ORM layer because of performance (and it still struggles).
I haven't used pydantic's ORM integration, but I don't hesitate to use pydantic models everywhere as business logic classes unless I need ludicrous speed.
That's all opinion, but I'd definitely give pydantic a swing.