N8 is the Asian version of the super popular poker room GGPoker. Both skins work on the GG Network and, as a result, they are virtually no different – their clients’ lobbies and functionality are really very similar.
The main difference between the two rooms lies in promotions. Natural 8 is are focused on Asian countries and players from there, while GGP is geared toward European poker enthusiasts. It's also the same reason UK players can’t play on N8 – they should use GGPoker skin.
Also, the poker rooms’ tournament grid varies somewhat. For example, Natural8 offers Hourly Freerolls, which are not on the GGP schedule.