I have a requirement to send 10 million records to Salesforce from a Mediation System. I can write the records in CSV in the system. Should I upload these files using DataLoader with Bulk API on , or should I make call from Mediation System itself to Call Bulk API Request?
If you have already a CSV file and it is a one time thing then i would indeed use dataloader with Bulk API option on.
It is easy to use and it will go quite fast and if there are any errors you will see it in an error file.