Whether an auto box holds on a hill actually has nothing to do with how good the box is!
The box is sitting there with 1st gear engaged waiting for you to drive off, just as a manual gearbox would be in the same situation. The reason that there is any creep or "holding" capability on a hill is because there is some torque coupling through the torque converter to the input of the auto box at idle speed. Unlike a clutch, a torque converter cannot completely disengage. If it happens that enough torque is transferred to hold you on the hill it's an unintended side-effect of how your torque converter works, not a driver aid or a sure sign that you have a "better" gearbox. Go to another hill and you might be creeping forwards or rolling back because the torque converter doesn't "know" how steep the hill is.
Another car will have different weight, rolling friction, idle speed, torque converter characteristics and 1st gear ratio, so it would be very unlikely to behave the same way.