with ADSL2 the speed is not always what they say, same with cable, but with cable it don't matter if you are 10Km away from the exchange or not, but with the ADSL more far you go from the telephone exchang slower the speed.
i'm not sure or the reability of the line, but my cable connection drops dead every now and then may be 1-2 time a month but thats about it.
with ADSL2 its easer and cheaper to install since its using your telephone line, with the cable you have to get a technician to come to install the line from the telephone pole then to your house and install the modem.
thats my point.
i'm sure that whirlpool
has more on this topic