The Netgear router is just a router, you would need a separate cable modem (gateway).
Although it may be convenient to have one box that does both functions, it limits your ability to upgrade economically and also is more of a headache if it fails.
You would have to check the Xfinity website or call their customer support to verify what modems are compatible with their system, cable providers vary as to how liberal they are with customer-provided equipment.
If you're looking to future-proof your setup as much as possible you'll want a router with dual-band wifi and the highest bandwith (AC is currently the fastest available) and gigabit wired ethernet, and a DOCSIS 3.0 or 3.1 modem with the maximum number of available bonded channels.
Of course all this depends on a few things like your budget, the current and expected future capabilities of your cable system, and as mentioned what modems they will allow.
I've been very happy with Netgear routers, I've had a few of them and they have been very reliable. Never need reboots and the user interface is very easy to use.
I recently upgraded my modem to a Motorola DOCSIS 3.0 16x4 (that's the # of available downstream and upstream channels) with a max download capability of 686 Mb. I think it will suit my needs for some time to come, my cable system doesn't currently provide those speeds and probably won't for a while (and I don't need their fastest service anyway). There are plenty of similar modems on the market from Motorola, Arris (basically the same thing) and others so you shouldn't have trouble finding one that works for you unless Xfinity is really picky.
One note about the DOCSIS 3 modems, even if you don't have the fastest service the bonded channels give you a bigger pipe for more stable downloading and streaming.