I have a nano Rings, it's not the one from After Later Audio, although mine has the same dimensions and layout.
The obvious difference is the size of the module and the knobs. In my opinion, the knobs are still okay to twist in a live jam to make it sound more or less 'big', achieved by modulating brightness (BRT on the nRings panel) and damp (DMP on the nRings). I do need to mention that my nRings is quite on the right side in my case, which makes it easier to access these controls. It would be more cramped if you put for example a mult or mixer to the right of the nRings, or any other module with a lot of sockets on the outer left of the panel. So some planning in this is advised.
The original Rings (and most clones I guess) are difficult to tune while jamming, as mentioned by Jim. This is because both the frequency and shape knob influence the tuning. There are some blogs/videos online on how to make this process more easy, Lightbath seems to have a good one I believe. I guess tunig is more difficult with the smaller freq/shape knobs. I don't have the original rings to compare, but if you tune it beforehand with some explanation nearby it's not impossible. However if you intend to change the shape while making music with it, go for the original rings.
(off-topic; I once saw a post somewhere with a modified version of the Rings firmware, which sort-of fixes that turning the shape knob makes it go out of tune. Haven't been able to find it since. If someone has a link to it, please let me know!)