Used to be upside down, facing out for the longest time because I just did it without thinking. Came to my senses a little while ago and do upside down, facing in now. I have a case so the outside is protected, the screen is protected from cracking (banging into table edges, etc.) and I don't need to adjust my grip from pulling it out, to using it.
The people I don't understand are the ones that keep their phone on the opposite side to the hand they use (i.e. right-handed but keep phone in left pocket).