Stickyback Velcro Application
When attaching velcro, my thought process is - when the two items are separated, which one would it be more pleasing to have the fuzzy side or the scratchy side?  Using velcro to mount a flashlight?  Fuzzy side on the flashlight for sure because it's soft.  Normally it ends up being scratchy side on the fixed surface and soft side on the portable piece.

You might also consider which side would pick up more dirt or dust when they are separated.  They both stick the same and have the same forces acting on them when attached, so my decisions focus on the separated items.