Low pressure, with a good degreaser and a brush will give you safer, and more consistent results... Than a blast at the QUARTER machine... Plus the high pressure wash pushes moisture everywhere and also has a tendency to remove any loose paint or labels in the engine bay...
Also I would recommend doing it on a day where it is warm enough and / or can be driven for a decent distance to heat up and dry out the remaining moisture in the engine bay.
That being said... on the PRO5 I would keep the water from pooling in the top of the valvecover, as well as the battery, fusebox area.
I have been stranded before upon restart while degreasing engines at a car wash...Now I make sure to keep the car running during the wash...