It depends.
Cable if you only care about pure download speed, and aren't too concerned with some downtime and higher latency pings. The cable is also good if you are sharing the connection among computers, as its IP is fairly static. (they just changed my buddies, screwed up his ip masquerading firewall until he figured out what was going on!)
DSL is good if you want reliability and reasonable speeds. With the new Alcatel platform that Sympatico has rolled out for their DSL service, it is ROCK solid. Ping times are also lower than cable.
I personally have cable, but if I didn't need to share the connection amongst computers, I would have DSL.
In terms of download speed, you can expect about 120KB/s downloads with DSL and approx 200KB/s download with cable.
Another thing to consider is the network each service runs on. Bell's network is one of the fastest and most modern in the world, with redundancy (incase of accidental fibre cuts) coming out the ying yang. The @Home network (cable) doesn't have the redundancy. In fact, the other day, a (single) fibre was cut in the @Home network around St. Catherines. Myself and the rest of the Ontario @Home users had no service for the better part of the day.
All in all, it just depends on where your priorities are. Whether it be brute speed, or reliability.