I trained out in the states, so will naturally be biased toward the way the training was carried out there. In 1995 when i trained, the autos were done to power recoveries at a 5 foot or so hover height. The only autos to the ground were done to with students who were doing their CFI course. On the other hand, as soon as autos were introduced to the PPL student, throttle chops without warning were also introduced - from my understanding something that isn't done in the UK so much.
The thinking behind this was that the entry to (or failure to enter) the auto is the thing that would be more likely to kill people. If a flare could be carried out to a power recover in the hover, then if it ever occured for real, the final 5 feet or so would be surviveable, hopefully with the aircraft still in one bit. This was thought to outwiegh the likely cost due to damage to aircraft if all practice autos were done to the ground.
I'm not sure what the actual stats are for comparing accidents involving engine failures between countries that put the emphasis on training for the unexpected engine failure, and those that emphasis the auto to the ground. Might be interesting to find out. I'd be inclined to think that the biggest killer would be caused by a failure to establish the auto quickly enough, and not be able to recover the decaying RRPM. As i said though, i'm biased toward the training system that i experienced.