Ok, so my answer uncalled for. When you asked about the "up carry." I thought you were refereeing to:Link Removed
In this picture, the actor specifically poses with the firearm next to the head. To bring the firearm into play, there is a lot of arm movement, and not very safe. Looks good on film, but..... I had a friend who tried this with a revolver, and he blew a hole in the roof of the range. Needless to say, I'm not a fan of this "carry."
The carrying of the pistol close to the body, and punching straight out to fire is more effective, but does not work well in all situations. Especially if you are surrounded by other individuals. When accompanied by others, a SUL carry "may" be more effective and safer.
Best answer, try different positions, low ready, SUL and others, and remember, not everything works all the time.
Bottom line, anyone can be an @zz (including myself), don't take everything you read as gospel, and be safe out there.