Thanks for your question. Orbi is a closed system with its router/satellite(s). It uses a dedicated FastLane3 backhaul connection between the router and satellite to maintain fast wifi. Since both router and satellite are both within a closed system, it can also do active steering of clients.
Nighthawk X6S Extender on the other hand is a universal extender. It employs some of the great features like FastLane3 dedicating its backhaul to the router its connected to. Also you can do single wifi network with One WiFi Name and Smart Roaming which helps clients to move.
X10 router has some great features like Plex, 11ad, port aggregation, QOS etc. which you can continue using with EX8000. You also have options of configurability of multiple SSID with X10/EX8000. The 5G band on X10 is a 4x4 so that's also a great addition. However keep in mind that this 5G band may not be dedicated from router since you can connect clients on 5G on X10.
