I don't know much about DSL, but I'll tell you about cable. Cable CAN be very kewl, when it works, which frankly isn't all that often. I have had downloads approaching 800KB/sec (note the big B there

). The average I've seen from my teching experience is around 200-300KB/sec, when it's working. That's a darn good deal for 30-40 a month. There are 3 primary problems with cable.
1. Upload speed is usually capped at 128kb/sec (note the small b there). Eventually all @Home upload will be capped at 128 if it isn't already. It's got two purposes: a: prevent people from running servers. b: reduce upstream noise to the headend.
2. Cable goes out a lot. It depends on your area, many people don't have any trouble. For others it takes 3 months to get hooked up correctly and then they go down every month for a week at a time or worse. I'm with @Homes tier 2 tech support and I've spent 4 months out of 9 either with no service, or with terrible connection, and I know what's going on and how to fix it.
3. There is NO customer service with @Home to speak of. @Home absolutely doesn't exist for the customer, they're there for the money. Now, that's a little simplified, there are other problems (like the individual cable companies trying to run something they don't understand) but it's important that you expect no support if you go cable. Cables rules are terrible, the cable companies are conglomerates with no knowledge or compassion and @Home is mired in so much red tape they might as well not even exist.
Any other cable questions feel free to ask.