Cable modems typically offer similar or slower speeds for downloads as DSL lines, when the cable infrastructure is new or well maintained. However, cable has a many disadvantages to DSL.

The first disadvantage is that cable is an RF network -- this means that it is vulnerable to transient problems "within the network" from RF interference. Since cable is a shared media, there is a possibility that performance may degrade over time as additional households plug in, connect additional devices (videos, game machines) to the TV lines.

A cable company may react slowly to decreases in performance, as they never sell access by speed or promise consistent speed or latency.

One of the largest disadvantages of cable over DSL is the upstream (return path). Cable companies are using a very narrow band for return signaling, below all the space allocated for TV channels. This band is prone to RF interference and is very limited in capacity. Upstream transmissions may therefore compete with others in the area, get delayed (suffer high latency) due to noise fighting techniques, and cable Terms Of Service typically prohibit any kind of constant upstream use. Internet use is shifting away from central servers broadcasting to many individuals and some interesting peer to peer applications are appearing (games, voice and video applications, web servers, remote access, communal libraries). These applications need a strong upstream channel.

In summary, cable modems are currently strong competition for residential casual use. However, DSL is probably the more future-proof system, offering digital direct from the internet infrastructure..