we have purchased our own, the additional capabilities (built in usb for network shares, static IP, routing control ect) are worth it for me, plus then i have full control over my local network.
the router side of the Xfinity modem is very well equipped.
reverse DNS for incoming (assuming you have a domain),
lots of rules to allow/deny,
assigned and dynamic IP, partitioning, multiple SSID for wifi.
So I think I'm good with it.
I'm running my eero mesh in bridge mode -
the UPS is on the cable modem/router and first eero - so two different networks stay alive between PF and the generator coming on-line.
it was really setup for my spouse to WFH and not fail. although she had to tether from the phone a couple times.
not so important anymore, but the h/w is in place.
I can't believe i'm forking over $250/mo to Comcast.....