Hello @Mat_Jung
in case of a bare MongoDB nothing. But when you look on Altas, you have fully automated deployments, professional backup, auto scaling, monitoring, suggestion of schema improvements, suggestion of index improvements, integration of charts, integration of MDB data lakes… So there is plenty more which can ease your live. In case you have some years of experience as MongoDB DBA and deployment and optimizing shards and replicasets and when you have already a working monitoring for MongoDB on AWS you may come close to what Altas provides. Minor updates are applied in Atlas automatically one point which saves quite a bit of work…
I am not a sales rep, so I may have missed some points. But again, I like to encourage you to read the linked pages and than make your decision. Feel free to ask any concrete question here in the community, we will try to answer. In case you need further input concerning you initial question I like to suggest to contact MongoDB sales - they will find you an optimal solution.
Cheers
Michael