Given that the USB port is useless on the Gateway, what “critical” services/feature will I lose by switching to my own router? I want to have a harddrive connected to the network.
You will probably gain some new features that are not supported by Comcast Gateways.
I use the XB6 only because I am cramped for space and if I got my own modem, I would have to add a box for Comcast XHome. (Some retail modems have Comcast Voice which would save me another box)
You would lose some pay-features like the remote-control 'xFi' stuff as well as rather excellent comcast apps/GUIs/software. I opt out of it all since it costs extra but I am always impressed by their software & system offerings. Many of the xfinity features are available for free in various aftermarket router/wifi/hubs, along with some extras. It's case-by-case pairwise comparison between whichever revision xfinity router/wifi/hub and whichever retail router/wifi/hub you are considering. Consider to obtain a side-by-side comparison of full-feature-lists for device which you are comparing and possibly highlight the features you care most about. Also it is most versatile for future-proofing and testing to own a cable-modem as a separate device rather than integrated into your owned router/wifi/hub.
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