I have soon Cable & DSL and i gonna see wich one is the best, but my bets are on DSL, not Cable.
Cablemodems are shared lines with you'r neigbours, and the router somewhere in you'r block is used as traffic by the whole neigbourhood is needed.
Speeds ETC are all depenaqble by the equipment provided by you'r ISP.
In my case this is now, an total useless connection for UT.
Few weeks ago, i still was the one here on PuF with the fastest cablemodem. Even faster as most DSL lines here, but now local dutch server win 700+ ping, and 20 to 90% pl constantly.
DSL is an dedicated line, totally of you'r own, no matter the load of the provider, it will NOT affect you'r speeds.
Also DSL in an Synchrome signal, with results in a more constant dataflow. With results in a steady ping in UT, not as with cable somewhere between 25ms and 300ms as i had allways.
Furtermore about Highspeed rig's, Yeah the difference between an P2-400 and a P3-550 isn't that large, specially with a good graficscard, but try to take it on with an P2-400 against a P3-850 with a Geforce2 in it.
I have such a setup on a LAN, so connection is not a issue here, equal pings, but man, when i play on my p2-400 and my GF on that P3-850 Rig, i totally get 0wned, but when she's playing on my PC, and me on that p3-850 rig, i 0wn here, badly.
And to be honest, i can play UT better as her, so PC's count as well, not only pings.