I think we're talking about a couple different things here. If you're getting a USB Cable Modem (i.e. the modem plugs directly into the USB port), then I can't comment. If you're getting a modem that plugs into a NIC (which is what Road Runner gave me), then I found the PCI NIC much more stable than an external USB NIC. My Netgear NIC was ~$18 and has worked flawlessly. Yes it takes up a PCI slot and may require a little tinkering, but the CPU cycle issue is so minor that I doubt you'd see any performance difference between the two (I didn't).