If a 10 would be a perfect flawless freecoaster, I would say the Ezra is about an 8. I would give Nankai about a 6 because the shaft breaks pretty easily and I had to regrease it every month to keep it spinning well. The KHE Greyhound would be about a 7 for me, I never had problems with it except a little excessive side lash in the bearings.
Remember, this is just my opinion so no need to start flaming.