A living car would be nice because it could drive you around so you don't have to drive. But a living house just sounds more powerful. Especially if it can move around rooms (like Harry Potter on a very small scale or event auto-renovate) or at the very least close the blinds and turn down the heat (like a smart house).

So, assuming that this house/car is benevolent, or even better your servant, then I would totally go with the house.

On the other hand if the house/car is evil (or turns against you)... I think I'd still go with the house. Even though the house would be more powerful and would cost more money to abandon... it can't move. Unlike a car, which can track you down and "get" you when you least expect it.

So, either way: house.