here are the facts:
Cable is shared on a line with other people, where DSL isn't.
Because of that shared line with Cable, your connection might not always be top par.
Most DSL lines run at 384k connection speeds, where Cable runs at either 512k or over 1MB connection speeds.
Overall Cable is faster but not as reliable. DSL is slower but more reliable. Both have their pros/cons.
I have DSL and i usually get about 110 ping on some of the crappier servers. Yet on that same server Cable users might be getting around 80.
On the other side of the coin, if you are wanting to host a server, then Cable is your friend. Cable can host up to around 8 players while maintaining playability on the server. DSL is lucky if it can support 3 or 4, and thats pushing it.
Now you can see why i dont host alot

.
Hope those bits of info help you out.