Features are the same across all hardware when running the premium firmware. Generally speaking, WRT1900ACS is faster than the Newifi-D2 we had earlier, which in turn is faster than the C7. Our new WiFi 6 router seemed to have better WiFi performance than the WRT1900ACS.
If you want to connect wired access points, then WRT1900ACS and our new WiFi 6 routers are better choices.