It depends on the technologies you're comparing as well as the local situation. But generally speaking cable connections use a shared connection to a nearby hub. As such you can get bandwidth contention if everyone in the area is making heavy use of the internet (torrents, major sporting event, etc.). This can also happen if the cable company has sold more cable connections than the local hub adequately supply (i.e. oversubscription). Compare that to an old style ADSL line where the copper cable ran from your phone socket directly to the local telephone exchange, which could be miles away.