I used both services so I can give you the pros and cons.
1. Comcast packages cable TV and broadband
2. They are now packaging VOIP which I currently have ATT VOIP. Thinking about switching when the price drops for Comcast.
3. I get speeds up to 36 MBps when I am wireless at this coffee shop in Oakland City Center.
4. Comcast is a bit high. I don't understand why they reward newbies when they have loyal customers they are screwing by keeping their rates high. It was like this when I was a loyal customer with Earthlink and they put the screws to me. They no longer get my money.
1. Comcast has no dialup service to my knowledge so if you can't get WiFi, you have to go with a freebie 56K service.
2. ATT/SBC formerly/Yahoo really sucked in service department. They literally used outsourcing service which I was convinced was in India. They could barely understand english let a lone the technical issues to get you hooked up.
3. You literally can go for days without human contact if you use their internet help. I pretty much had to figure out the DSL issues on my own.
4. Some of the DSL problems were with wireless in my apartment. Put the wireless receiver near the Computer Monitor (tube type monitor with huge transformer knocs out wireless).
5. Comcast had its problems. When I first got service, I had to call out service 4 or 5 times since the digital signal was so poor, it was marginal and really impacted my digital TV signal. There are no amplifiers so you have to pray to sort out complex wiring of a large home. I was sharing wiring with my landlord.
6. Since I live just 20 miles outside of San Francisco, I get more expensive Comcast service. The folks living in the City have it better with concentrated market but they have to put up with urban scum and psychos screaming at the top of their lungs on the street corners!!
I saw a TV program with all the top CEOs (Comcast, ATT, Disney, Cisco,etc) saying they are going to rule the world when they can bring the internet and TV experience wherever you go. I've been waiting for five years now but can see the improvements over time.
Hope this helps somewhat.