There are two ways to shut down with the power button. Press it for a short duration and it should go through the shutdown process. Hold it for a 3- 5 seconds and it will shut off hard, often without going through the shut-down process. But my unit has gone through numerous power outages where the units were not shut down properly and all have been just fine. In normal operation, there is no data that is being held in a cache and needs to be written to the hard drive. So it shouldn't matter that much what process you use.
I say this with a caveat...these are basically purpose built computers and like all computers, once and while they don't behave as expected.
- Jim