@DanielPereira 

This is true: if you wire all X90s with Ethernet cable, and wire them correctly so that they can use Ethernet backhaul, there is not much difference in their performance comparing to X60s. 

----------

Except one special case, based on the fact X60 has two gigabit Ethernet ports, but X90 has one gigabit and one 2.5Gbps Ethernet ports. 

If all your X90s run in Access Point mode, all have their 2.5Gbps port connected to Multi-Gig switch (see https://www.netgear.com/business/wired/switches/multi-gig/) which in turn connects to ISP router with 2.5Gbps or faster Ethernet port - then such setup should perform better than X60s under heavy load.

Note that connecting 2.5Gbps Ethernet port to just "regular" 10 gigabit switch won't give you anything better than 1 gigabit speed. A switch that understands 2.5Gbps and ISP router that has at least one 2.5Gbps or better port are required.

-----------

For the rest of us, mere mortals, if you can wire all your Deco X** units, you could save few dollars by downgrading from X90s to X60s or even to X20s, depending on what coverage you need. In fact, if Ethernet wires are plenty everywhere, having more X20s in strategic places instead of fewer X90s here and there would be better for WiFi coverage. For the same hardware price.