Other than just speed, think about other services that the ISP offers such as number of mailboxes, newsgroups, static/dynamic IP, etc.
As for me, DSL and cable are both available in my area now. From what I have heard, cable in my area is faster than DSL, but I'm sticking with my DSL because of newsgroup access. @Home news servers (from what I have heard) are very crappy. I also like how my ISP (Verizon), lets me connect multiple computers to the DSL line through a regular hub without a router. Costs wise, cable is about $5 cheaper, but I have to buy a modem.