Note : I am using paid version of it so having all features enabled for me.
Powerful support for replica set and various auth mechanism.
Inbuilt shell (intellishell) for writing custom query
Separate interface to build pipeline for aggregation operation
Map reduce, schema compare, schema analysis, sql to mongo query conversion, backup and restore are the other features which reduces our daily effort on multiple tasks.
Connection management will be the best you would find in this if you are dealing with multiple server on your daily routine. For me I work on microservice architecture so I am having huge list of server and database. It does allow tagging a color to every connection so you would tag your production in red color to prevent accidental damage to it.
Inline editing of documents, without blocking the main ui (unlike mongodb compass which blocks the user action during load operation).
Trial version is limited to only 3 connection.
When you open any collection you can access query window till the data gets loaded, reported already to team but no update on the same yet.
I run IT service business, where I have to serve multiple clients. Studio 3T allows me to manage all my database in single interface thus increases my productivity.
Most importantly I can manage even all my production instance including all replicasets.