When comparing Disk Inventory X vs Notational Velocity, the Slant community recommends Notational Velocity for most people. In the question“What are the best power user tools for macOS?” Notational Velocity is ranked 11th while Disk Inventory X is ranked 52nd. The most important reason people chose Notational Velocity is:
The interface is clean and unobtrusive.
Ranked in these QuestionsQuestion Ranking
Pros
Pro Free & Open Source
It is absolutely free and released under the GPL.
Pro Works in High Sierra and above
Pro Allows ordering disk by size
This way you can find what is taking most of the space.
Pro Offers choice between analyzing whole disk or just a specific folder
Pro Absolutely matching with Windirstat
Pro Simple and minimalistic
The interface is clean and unobtrusive.
Pro Free
Pro Syncs with SimpleNotes or Dropbox
Cons
Con Crashes on Ventura, when closing the app
But you do not need it so often, so it is ok.
Con Crashes on Sierra
Crashes on Sierra when resizing windows.
Con Feels a bit outdated
The last release was from 2011. Although due to its brilliant simplicity in doing what it's designed for, some might think there hasn't been any need for an update, as long as it still works with the newer OSs.