Oh god.... Another flaky digital cable thread....
They make NO difference. So long as the cable supports the ethernet configuration, it makes NO difference. This stuff is obvious. I can't believe people come here and debate this stuff in a serious way. If you think you're hearing differences in your purely digital cables like your HDMI and ethernet cables, it's PURELY in your head. Go read the actual specifications for these interconnects. I have. Nobody who knows how this stuff actually works would conclude you can hear a difference. The actual "sound" is buried under layer upon layer upon layer of physical layers, electrical layers, and protocol layers. It's being packetized, unpacked, routed, and decoded by millions upon millions of MOSFETs stuck to tiny copper traces through far-less-than-audiophile grade leadless Rohs-compliant solder. And some of you think you can "hear" a difference! Can you hear the difference between different brands of tiny surface mount termination resistors? Can you hear the difference between a .3 and .4 volt LVD bit? Where exactly does your insanity start and end? Are the squirrels on the cable up on your telephone pole injecting noise into your digital signal? Are those audiophile-grade telephone poles? What if the wind blows from the north instead of the west?
And by the way, I think it's very foolish to hardline anything to a broadband modem that you care much about, ESPECIALLY a coax cable modem. Coax is like a freaking lightning rod. I've been running cable modems since 2001 and I lose one to a lightning strike about every 18 to 24 months. I just had one replaced last week. If you MUST hardline your intranet from a cable modem, by all means get the most robust surge suppression you can find for that coax. I've seen strikes rip through the modem, the router, the switch, and every network card connected to it. Unless you NEED the speed, go wireless.