VTX (www.vtx.ch) is an ADSL provider I have used for one year now in Basel. I use them for primary phone and broadband. Their customer service has been excellent and flexible. I do not use the router they provided, but rather my own router.

I also use cablecom for secondary phone line and broadband backup. My router provides for backup WAN connection as well as for load balancing.

Personally, I would not use cablecom for broadband if I did not have my own router/firewall between their cable modem and my home network. The cablecom network is not as secure and has more broadcasts, DoS attacks than VTX.

For ADSL, I would never use the incumbents (PTT) retail service. Rather I would always find a reliable private company such as VTX. Swisscom, like any PTT will likely filter traffic. Private companies buy their capacity wholesale, so have control over the retail service delivery. VTX does not filter any traffic.

It is also important to note that when comparing cable versus ADSL solutions, within a market (eg. Switzerland) they commonly share the same wholesale providers. The differences are in the medium delivered to your home, price, quality of service (for the retail side of the network managed by the company) and customer service.