Both suck.
Between Comcast cable and Verizon DSL, I'll go with DSL. We have it at the office and it's not down at all that I can remember, well maybe once. With comcast at my apartments it'd go out randomly and stay out for hours.
I have Verizon FIOS 15mb down, 2 up.
FIOS > Cable > DSL as far as speed, depending on the packages. FIOS also has a 5mb package and a business/home package for 180 a month.
FIOS > DSL > Cable as far as reliability.
Not to mention the fact that FIOS is the only absolutely TRUE point to point connection between the Central Office and your home. Sure DSL runs over your phone line, but the bandwidth is nowhere near guaranteed. Get on Cable around 3:30 in the afternoon at home? Yeah, you're fucked now that all the kiddies are home and gettin on the net.
Not only is this my personal opinion, it's also what I've noticed from a professional standpoint. Constant frikken Cable outages which the customer will call us and complain even though it's comcast.
Then you have the straight shot T1 and T3 connections.
I love stealing that bandwidth when I'm driving around with my laptop.
On top of that, i think I'll vote DSL. You get a landline which is about 15 a month, and the DSL service is about 30 a month. You may not get the speeds of Cable, but you're paying about 20-30 less a month than you would with Comcast here for, IMO, better more reliable service.