Going to stir up the pot lol I have always put my hole on the bottom, I guess my thought was always if something catches it, the pipe is sitting on top the screw and less likely to come out of the strap and off the wall. With the hole on top if something catches the pipe it could get popped out of the strap.
But really, if anything catches the pipe, up or down, it's probably getting pulled off the wall regardless. I usually will reach of Mini's first before a 1 hole strap anyway. Or strut and strut straps when over 1".