Obvious advantages of the Innuos are what you’ve stated: disc ripping, audio outputs built-in, and that it comes with storage.
The big issue is with the CPU. The CPU in the Innuos Zenith mkII is below the specification we suggest for Roon. The result is limited library size, limited DSP functionality, and slower searches/focuses/loads/etc… Nucleus meets our suggested specifications, and Nucleus+ greatly exceeds them.
Innuos has an option to turn off the Core and just use it as an audio/storage/cdripping device. The CPU issue disappears if turn off the Core feature, but then you can’t compare it to the Nucleus.
There are Roon members that use the Innuos for audio/storage/cdripping and use a Nucleus for the Roon Core all in a single setup. For example, @alex_wood posted that he uses the Innuos for CD ripping and a Nucleus for the Roon Core: