I've had DSL service here in Delaware since it started what, 4 or 5 years ago, and it's been great, more than fast enough & only down twice in all that time (once was a yahoo with a backhoe that dug up & broke a cable right next to the phone company switch office...).
OTOH, Comcast is much more hated here than the phone company. Rates have increased at least 5-7 percent per year without fail. I was at a customer's house helping them with their home network and the Comcast connection he had was Dog Slow. I mean really really piss poor. Maybe it was just his neighborhood ? Oh, and he had reliability problems too...
A DSL connection is your line direct to the phone company switch office, over your own wire, which dumps directly into their network.
Comcast is broadcast over a shared cable, so the more active your neighbors are the less cable bandwith you are going to have (it's a shared bandwidth system).
Of course all the usual disclaimers apply, YMMV, etc etc