If you just need to run a Python script on a schedule, then Azure Automation is likely going to be simpler to set up and manage and can run for more than 10 minutes, whereas functions cannot (unless you use the premium plan).
Both have a free allocation and fairly low cost for simple execution, but for your use case, Azure Automation is likely going to be easier. If you need more advanced triggers, more complex code or integration with other Azure services, then functions become more appealing.