I have SBC commercial DSL with Road Runner cable back up and everything works good - I have maybe two DSL outages a year.
One imporant thing I noticed regarding cable speed.......running zone alarm as an additional firewall to my Lynksys blue box with NAT cut my download from 7 megs to 3 approx, I kid you not. I went to dslreports.com and using their testing tools several times to see if it was a fluke. That is a great site. I was shocked to say the least! You can bet I don't run Zone Alarm whilst I am trading!I also tweaked my computer MTU for optimal settings based on my cable provider and it has helped about 10-20%.
I have had 3Mb DSL as a back-up for my RoadRunner (5Mb) for the past few years. Obviously, the cable was faster (5Mb vs 3Mb), but I just upgraded my DSL service to 6Mb for $28/month from AT&T one week ago. My router (Xincom XC-DPG502 Twin WAN Router) normally does load balancing between both connections, but I took turns disabling each connection last night to test them out with the speed tests at dslreports.com and the DSL is marginally faster now as expected. I haven't had a chance to test the differences in latency between the two, but, based on past experience, DSL usually wins in that department as well.
Went with AT&T last month and am consistently getting 5.5 mbps download and 515 kbps upload on dslreports.
In my experience it really depends on whether the company, dsl or cable, has decent LOCAL service ie when there is a problem they send a truck right away. With my cable service, if there is an area outage they know about it from the cable modems in an area all going down. Also near me Verizon dsl is operated by cretans. BUT THIS could be very different other places. I suggest you look by your zipcode here for feedback: http://www.dslreports.com/search
With comcast I am getting 4 mps, almost always. Its in Oregon so that may mean not much traffic. It doesn't change no matter what time of day. Stable as a rock.
Are you saying that your DSL is marginally faster than your cable connection now? I just went to the San Diego Fair yesterday, and was checking out AT&T DSL which had a booth. By the way, is it easy to configure your dual WAN router, or do you have to be a computer geek to do it? Thanks!
This can be used up to 3 times a month for free. http://bandwidthplace.com/speedtest/ I just ran my test here in Illinois....4.5megabits per second...I use DSL