People always say that dsl isn't shared, but that's a little misleading. DSL gets you a dedicated line to the ISP, true, but once you're there, your traffic gets lumped in with everyone else. So if they don't have enough outgoing bandwidth, you're gonna feel the bottleneck.
 
I would recommend you just compare prices, and try to find out the experiences of other people in your area. www.dslreports.com is a good place to look for user reports on various isp's.
 
Also, see if you can get AT&T to tell you what the speed of their cable is. I have AT&T Broadband, and they limit me to 1.5mbps/128kbps. And for just about every test I've tried, I get almost exactly that speed, so for me it doesn't appear to be overburdened. This is in Boulder, CO, so it may be different in your area.

Thanks for the info, the site was very informative. Anyway I got AT&T cable and the speed is incredible. I actually see 1-5MB all the time while downloading, but usually hovers at 400kb in explorer. Uploads are just as crazy. I hope it stays like this. I think its cause they got Boston covered with cable.