Logging: MogoDB vs RDB

Hello there!
I am working on a logging project. The goal is to demonstrate the benefits of documents over relational DB’s tables.
There is a central Linux server with MongoDB installed, a-so called inventory. It has an SSH connection to multiple other servers (they are virtual, so the quantity may vary).
I can collect and log whatever information is necessary e.g. CPU load, disk space, top memory consuming processes, any information from other applications (anything can be installed)
BUT
the point is that the chosen set of metrics must be stored in multiple tables on a SQL DB and would require a JOIN when retrieving. The MongoDB version, on the other hand, would keep everything in a single document. The frequency of data scraping doesn’t matter, however it would be great if those data were ‘visualisabe’ in a graph.

I am thankful for any ideas/advise/help
Thank you in advance!