I don't know how either of them work for certain, but neither my old MB or the Outback will roll back no matter how steep the hill is, it's a little disconcerting to be honest, i could release the footbrake and it would just stay there during a traffic light sequence on a max incline for instance but i don't.

I understand the MB box has a simple anti roll back device inside the box itself, must be simple mechanical/hydraulic its working perfectly at 18 years.

Compared to satans automanual and dual clutch things, TC boxes are all lovely to drive especially for hills requiring fine control, found the Matiz TC auto a little peach to drive.

It must be a combination of the design of the converter, idle speed and so on. I recently drove an Interceptor and that pulled like a frisky dog when the engine was cold and idle speed was about 1,200rpm (auto choke), requiring quite a firm foot on the brake pedal to stop it creeping.

When the engine was warmed up and idle speed around 600rpm, the creep was much gentler, needing only a light brush of brake. Don't know if it would creep uphill as I used to engage neutral when stopped at traffic lights etc (I know this is controversial practice with torque-converter autos :-D)