I finally saw the nano in person today. The only disappointment was how white and lighter shades of grey have a visible rainbow grain effect. The contrast and sharpness is very close to the glossy.
The rainbow grain is much worse on the iMac and M4 iPad nano screens; those have a pronounced dirty look that pretty much cancels out the high pixel density.
I feel pretty torn on the MBP, but would probably stick with the glossy.
I also thought space black looked pretty bad, almost like a plastic Dell vibe. Silver for me.