The people on here are funny they all have heard such and such from their friend but never have really experienced it...
Cable and DSL both heavily depend on the provider... I have dealt with Charter and Adelphia for cable co's and Verizon for DSL.
So far I would have to say cable is a bit less reliable though ussually has highier download speeds and costs more. At high traffic times depending on your area you will have to watch out for line congestion which leads to slow pings and slow connection speed. Now this isn't always true. My parents have never been affected by this where they live but where I live I have. Also with cable watch out for hidden download caps which they will not tell you about and will not warn when u are reaching near them to ban you permanently.
For me in the last year with Verizon DSL I have NEVER EVER had a connection problem. I mean look at it this way how many times have you said or heard some else say the cable is out? probably alot of times... which also means the internet is down if you have cable. Okay now how many times have u said or heard said the telephone is out? I personally have never heard such a thing other than in cheesy horror movies... Anyways for DSL it does matter how far away you are from the CO (central Office) or RT (remote terminal) ussually under 12000 ft you are pretty good for speeds and even highier it is really up to the company to decide what speeds you get out that far. I am relatively close to my CO and I get speeds of 1500/384 which is pretty good and later this summer Verizon willl be updating allowing for 3000/768 which is some big time upload speed... I also ussually have pings times of 30-40ms which isn't bad at all. It is also ussually cheaper and does not have any download/upload caps. The company's could really give a crap because you really arn't affecting anyone else.
Generally CAble Co's are stricter on thier ToS ( Terms of Service) IE. if you run a server they will boot you... DSL company's may have the no gaming server in the ToS but they certainly won't boot you if they even care at all... Some campanies offer better support than others and will actually try to help you while other just have a bunch of idiots on the other end of the phone.
I personally think you are asking the wrong question. DSL and Cable have thier strengths and weaknesses both are good technologies and always improving. The only thing that holds them back or pushes them forward is the company's that are running them.
So the real question should be "should I go with cable Co X or DSL co Y.
I recommend going to
Broad Band Reports once known as DSL Reports. Here you can research the individual companies and decide for your self from peoples reviews who have actually used the companies that are in your area and may even live in you area and see how they like their ISP. They have alot of information. Forums, speed test, broadband tweaking guides and news. Just please don't go by what a bunch of misinformed people here at Anandtech are saying. The cable vs DSL debate at this forum is about the only thing I think most people here are really idiots about and have no clue what they are talking about.
Sorry to the few of you that have a clue but there are some that surely don't. So go to Broadband Reports and take a look at a few reviews of the ISP's in your area.