Exclusive games with a decent bump in power compared to THE COMPANY'S previous gen. The NX will have its own unique features, games, and services when compared to the WiiU. That is what makes it 9th gen.
The Neo is a slightly more powerful PS4 with no exclusive features, games, or services. It will run the same games but at a slightly higher performance level. That is what makes it 8th gen.
Not that hard...