It depends... Roadrunner can be fast for me but slow for you; My experience with cable is as more people got it, it in turn got slower. I just had Comcast cable installed at my parents house for when I visit them and to do some slingboxing, I can notice that it was slower than my old cable access... the difference is:
1. Where I use to live, there was cable, DSL and Microwave (tall poles with square antennas attached to them that have to point to a main tower) Internet access. Where my parents live there is only cable (satellite too, but who counts that).
2. The section I lived in was lower class, mainly renters and was a few blocks from the cable company. My parents live in a middle class area with lots of kids. Chances are there are more people with cable access where they live than where I did.
From 6:00PM until around 11:00PM the speed is slow; more people on the service.
I would have picked DSL for there house if I could. Good thing about cable is there in not contract, if you experience issues like my parents you can always go to DSL later.