DSL offers "always-on" high-speed Internet access over your existing copper wire telephone line. Cable modems offer high-speed Internet access over a shared cable television network (like an office Ethernet.)

Cable modems can theoretically offer greater download speeds. But the problem with this option is that bandwidth is shared among all cable internet users in a neighborhood, this affects your download performance as more users in your neighborhood log in to the network at the same time - Picture a garden hose with one small leak in it. Then picture the same garden hose with hundreds or thousands of leaks. It's the same principle.

Upload speeds over cable modems can in many cases be slower than DSL, as well. Usually it's because too many people in a neighborhood are trying to send or receive data at the same time.

Also, since cable modem's share a connection there are security issues that must be handled by your server. Therefore, cable modem services often do not support a wide variety of Internet applications due to their ability to breach the security of other users and the network server. (Try using some of the free internet phone services, broadcast video conferencing or remotely controlling your computer over the internet via software like PCAnywhere... They just don't work over cable modems due to port restrictions.)

Enter DSL. Faster than cable modem service at peak usage periods; DSL has been found to be 11% faster than cable modems. Again, this is due to the fact that you are not sharing a network connection. Your DSL wiring between your computer and the DSL Access Multiplexer (or DSLAM - picture a huge modem) is yours and yours alone.

Internet applications are not restricted as they are on cable modem systems due to the fact that your connection is exclusive to you.