In short, standby does draw some power to keep the system running.
Hibernate writes all data in ram to disk and than restores back to that state on power up.
From what I've heard people say on this forum, if you have a good battery in your car, you can expect it to kill your battery in a few days. Probably even faster during harsh winter months and weak charging systems.
I've had a problem with the longer the computer has been in hibernate the longer it takes for the computer to recover. IE if I don't drive the car for a week it can take several minutes before the thing wakes up out of hibernation. But if the hibernation is only for a few minutes the computer wakes right up. Do any of you guys have similiar problems? I'm currently running an old K6 550 system either a sis or via chipset (I can't remember) but I plan on replacing it shortly with the epia board.