9.0 has just been released so there might still be some minor issues with all our favorite tools.
8.0.1 has been out for quite a while so every major issue has already been resolved.
Call me lazy but there are no games that require 9.0, so imho no need to update to it.
Some recent game updates require 8.1.
Maybe familiarize yourself with ChoiDujourNX to update to 8.1 (and 9.0 in the future).
And do make a full NAND backup just in case something goes wrong (most things can be fixed by reformatting the SD card and do a clean install of all tools).