I have been on both, Cable and DSL.
Cable is generally faster, however, it FLUCTUATES in speed, some hours your faster, some hours your slower. Data is not a nice stream, it's like chunks of data coming through. It has higher burst rates.
DSL, is stable, solid, and never fluctuates, however, the speed you get, depends on how far you are from the Central Office. You will always get that speed after which.
For general downloading and browsing, Cable is more cost effective. If you're going to do gaming, and need something more stable, go for DSL. Lower latency ping rates, and data that don't fluctuate. Definately much more stable.