You get what you pay for.
If speed isn't your end-all, be-all, then DSL is probably a better deal (although there's probably a one-year contract involved, which is something cable doesn't have). As a rule, DSL is slower than cable, and often by a material amount (factor of 2+, in many cases). On the other hand, though your cable connection may offer 6Mbit down, if most of what you do is web surfing and the occasional file download, you'll never actually hit that number, anyway.
If you're a gamer, speed is somewhat more important, but still not critical. Higher throughput generally goes hand-in-hand with lower ping times, but not necessarily. Besides, for most broadband ISPs, the bottleneck won't be at your end, regardless.
If you're a music/movie/file sharer, cable is well worth paying for. Once you start splitting your downward pipe five or ten ways, the extra capacity offered by cable really starts to shine.
The other thing to consider as far as cost goes is the associated costs. For example, in my case, I've elected to go cell phone only. Not having a land line, if I wanted to get DSL, I'd be paying for the phone line, basic service, and DSL, all of which will add up to more than I'm paying currently for my cable internet connection. Of course, if you've already got the land line and plan on keeping it, that's not a consideration.
On a side note, it's amazing to me how much money you can save by just ditching the phone company. Given that I wanted to have a cell phone anyway, it's a no-brainer in my book. And so far, the only problems I've had by not having a land line have been with a pizza delivery joint that won't take cell phone orders and a mom-and-pop video rental store that needs a land line number for their application.
Well worth the $30+ a month, IMHO.