Which is better, Xb6 or xb7?

I’ve recently upgraded my tv/internet package and received an xb7 gateway. I was excited at first but I’ve been getting speeds less than 50% standing within a few feet away from the gateway. A customer service rep said they’re putting in a ticket to send me an xb6, but to me it seems like a downgrade. Has anyone had experience with these gateways and what was your experience with the WiFi speed? Thanks in advance.

FYI I’m supposed to be getting 600mbps but since receiving the xb7 I haven’t gone over 500 and the speed usually Ranges as low as 115 - 440. Again this is within a few feet of the gateway