Roon Nucleus vs generic NUC

You’re not missing anything. If you want, you can put your NUC in a fanless case. Otherwise, no difference. 

the roon nucleus was a huge disappointment in my system i sold it and moved on. just open the box and look inside your phone has more in it then the nucleus. but seriously its not worth the money. lackluster sound at best my optimized PC was better by far. I'm sure your current NUC will out perform it. To be honest the bluesound node is just as good if not better as a streamer, obviously lacking the roon software.  Only reason you buy a nucleus is you need roon and are not able to set it up on another device.  personally i didn't like Roon but I'm an outlier i suppose.  I'd say even my Apple 4ktv box is about as good as the nucleus streaming Tidal (cd quality). 

I moved to an Aurender A10 its better then the nucleus but really not better then the optimized PC i was using prior, IMO waste of money, put the money into the  DAC IMO.  

I had pretty much the direct opposite experience. Prior to using the Nucleus, Roon core was on a MacBook M1. Pretty good SQ in my opinion, but hadn’t known how much noise it was introducing until I had moved the core over to a Nucleus with a separate streamer. This was unexpected, especially after reading many post on this forum and the Roon forum. I guess like all things in this hobby, your experience may very and system dependent.