RF or Bluetooth?

Hello everyone!

I'm brand new here, and new to Arduino in general. I'm just starting a project and could really use your help in deciding which components to buy to start testing the concept.

The project is basically an RFID reader that controls the ignition of a car at a rental house. The RFID reader needs to communicate with a computer in the house which is connected to the internet. I want to go online, access the computer remotely, and specify which RFID tags are allowed to start the car. The base station needs to communicate the allowed RFID code to the reader in the car, and delete old RFID codes that should no longer be allowed.

I'm planning to use a Arduino controller to run the access programs, RFID reader, wireless interface, independent power source (probably a rechargeable battery), and link it all into the ignition system.

I'm pretty sure I can send new codes and delete old ones using either RF or Bluetooth (please correct me if I'm wrong), but because I'd like this to be as secure as possible (it is a nice car), if RF is easier to hack than Bluetooth, then I'd want to use Bluetooth, but if there isnt much of a difference, I'd rather use RF, because its cheaper.

In addition, because sometimes the cars are sitting around for a week or two the whole system needs to draw as little power as possible, and if possible wake up from standby to accept new signals from the base station.

Any help in deciding what I need, either for the wireless operations, or for any other part of the project, would be more than appreciated.

Thanks in advance everyone!