I had AT&T dsl for over 10 years, but left for Comcast for this very reason - speeds versus price. I was paying nearly $50 for a 6/.8 dsl connection, which gave me more like 5.1/.76 with a lousy 150gb/month data cap
We couldn't even get Uverse internetuntil fairly recently.
Comcast gives me a 20/4 tier for the same $51...and I actually get 22/4.5 speeds, not including
the "power-boost" bump (which I believe will be going away anyway. For the past year, Comcast has suspended caps, but when they come back, at least they will be higher than AT&T's.
If I went to Uverse 18/1.5 tier, I still wouldbe getting performance somewhat lower
than the stated plan.
Both services are/were stable here, however, Comcast support has definitely been a few notches above AT&T's support...though frankly no ISP customer support services is exactly "stellar"--
Deeds, not words