Hi,
First you should rule out the Mongo Datastore. Loading large binaries into Mongo doesn't perform very well and is neither recommended by Mongo nor by Adobe.
I would prefer S3 datastore but only if you are hosting at AWS. The hardest choice is on-prem hosting, because there S3 can be not attractive due to high network latency or for policy reasons. In that case I would validate the setup first by doing a proof of concept and running performance tests of an S3-based setup vs a FileDataStore-setup.
Remember: In the FDS you need to care about backup and restore yourself. And this can be problematic if you deal with tens of terabytes of data and a lot of files.
Jörg