Seems like everyone agrees...there is no definite answer Cable vs. DSL.
I recently switched from DSL to cable. Because the package deal was too irresistible.
Cable TV (a must), is what it is. And for what worked out to be an additional $5 a month, I get Cable modem (Adelphia, South Florida).
The DSL (Bellsouth) NEVER went down once in the time I had it (about a year). The cable is FAR less reliable. But the price makes it worthwhile for my home connection. However I would NEVER use it for trading.
Reason #231 that I have always, and probably always will trade prop. T-1 line (not necessarily faster, but totally reliable), and when things go wrong (never the connection as far as I know, but other problems occur), I like knowing there are backups, and people to call.
I realize that some people don't have a choice. Some locations, you may trade prop, and still have to connect from home. In that case, I suppose having both cable and DSL (when possible) is the only thing that makes sense. For the extra $40 or $50 a month, why take a chance? No sense to depend on any undependable technology when there is so much at stake. Besides, if you are trading from home, it's a deductible expense.
And as I have said before, I don't know squat about technology. But I know what makes sense in business. And skimping on a connection makes no sense whatsoever. BTW, with the Bellsouth DSL, you got an automatic dial-up backup just in case. So it was only a matter of waiting for the modem to dial. Slow, but at least it was something. So having cable, and DSL actually (at least here) would give you three ways to connect. I imagine it's pretty much the same all over.
Peace,

RS