"with cable you are more geared up for future developments"

Cable is already running near its theoretical limit - you can only carry so much info for each frequency and the cables are currently manufactured to be optimal for the current carrier frequency - while it can carry much more in total than what each consumer gets, the economics rely on it having that total bandwidth sliced up for all the users. You will only get more speed/throughput if each user gets a bigger chunk than currently, thus having fewer users, thus needing more cables.

Phone lines have nearly reached their limit - indeed although the recent ADSL/ADSL2 advances have increased the capacity, there are distance limits that cause the capacity to drop off with increasing distance - over a certain limit, ADSL2 does not work any better than ADSL can.