It all depends on how your cable provider implements the technologies. If they're using switched video, a cablecard is unable to send the tuning signal back to the provider, ergo, unable to change channels. Cablecards are a one-way only device as well, and prevents any pay-per view options. In general, the technology is considered a flop so far. On top of that, there's some wide discrepancies in how much the different cable providers charge for you to rent the cablecards. (Oh yes, it's just like the set top box, but without the box.)