I have both at home, so I'm in a unique position to judge both. I have Adelphia cable for my cable, 3mbs down and 256kbs up (it used to be 128kbps but they increased it due to pressure from DSL). The cable is fast! It will outrun the DSL any day of the week, although it is shared, I know of at least 2 people in my neighborhood with cable, but they don't seem to slow me down much. However, Adelphia has had more outtages in the past month than my sDSL has ever had in the 2 years I've had it, which is about once or twice. My sDSL is not with my local telephone company, BellSouth, but with some 3rd party company in Miami. I used to have aDSL be with Telocity which got bought out by DirectTV and then they dropped aDSL alltogether, and even then, it was rock solid in reliability and decent speed. I never liked BellSouth, one thing I love about DSL is your ability to choose who you want. You have a lot more options. I'm relatively close to the CO and I've had no issues. My next door neighboors have bellsouth DSL and say it's ok for the most part but their DNS servers tend to go down, or they tend to be slow at times, but that's the ISP's fault, not the technology.
So for awesome speed and quick install (less than a day), go with Cable. Disadvantages are the shared speed, which doesn't really affect much, and you get no options but your cable company.
For good speed reliability, and general overall better connections (my games like it more than cable, less packet loss, lower ping times), as well as the ability to choose your provider, go with DSL. I don't ever recommend the local telco for DSL. Disadvantages is the install time.
A tech once explained to me the technologies on a technical level. Cable is fast, but it's clumsy, it sends the data fast and hard with little to no regard for packet loss and such, it just expects that TCP/IP will compensate by re-requesting the dropped packets. Which is ok, but not so clean. To the naked eye you wouldn't notice it. DSL is a cleaner technology, it's got mechanism's for line speed control and flow control and all sorts of things, to minimize the packet loss, if any packets are lost, tcp/ip will re-request them and all's well. But he said a 3mbs cable will usually not perform as well in sensitive applications like VOIP or Gaming versus using DSL. He said that even an older/slower 128k/128k ISDN is cleaner than Cable. But you know what, I've recommended Cable to many of my clients and they have little to no problems, except the occasional downtime.
I usually say "try cable first, since you can get it quickly, if it sucks or goes down too often, then order aDSL, a month later when DSL is installed, drop the cable modem. Adelphia doesn't require contracts."