Uploading New List to Database - Use SFDC or Marketo?

Highlighted

Uploading New List to Database - Use SFDC or Marketo?

I am about to import a very large list of individuals (50,000+) into our database. We use Marketo and Salesforce. Is it recommended to upload that list into Salesforce, and then the individuals will automatically sync into Marketo? Or upload the new database members into Marketo first?