The main differences I've noted are:
1. The amount of vapor produced is roughly twice that of the N'Joy.
2. The taste available (I could only ever really stomach the N'Joy menthol, and I'm not a menthol fan!) is much better.
3. The battery lasts a lot longer, too.
I'm able to basically vape all day (8 - 10 hours) on one battery. I'm still experimenting with flavors to find the one that will be IT, but so far the pineapple is pretty darned good, with the RY4 a close second.