Six of one, half dozen of the other. You can rationalize any scenario. I carry my phone on me in a pocket that I could reach with either hand if I needed to due to injury (of course the pocket is easier to reach with one hand or the other).
I want the phone on me so that depending upon my injuries I can call from where I am lying and not have to move to get back to my bike. I have been primarily a dirt rider though nowadays I ride more dualsport and even some paved-road-only rides on my big bike. As a dirt rider I have been in hundreds of crashes and have yet to be injured by my phone.
I don't use a tank bag so can hardly keep a phone (or anything else) in one and that still would mean the phone is with the bike and not with me. I have been in crashes where my bike slid down into a ravine or down a hill leaving me at the top. Seems to me you could fall on your tank bag as easily as fall on your phone. As for packs, a belt pack in front might be easy enough to reach but I simply don't like one there while riding. And you could fall on that too! Back packs or belt packs in back are not as easy to reach and again you could fall on them.
It's almost funny how people worry about falling on their phone yet mount all kinds of stuff on their handlebars that is sometimes rather sharp, and they don't worry about falling on that. Or they have metal cases on the bike and don't worry about being injured by those. I have broken off handlebar mounted stuff with my body during crashes.
I carry a rugged phone in either a side, chest or pants cargo pocket as the case may be. On dirt rides I don't always wear a jacket (I have a rigid chest protector) but my dirt pants have cargo pockets. On dirt rides I will wear a Camelbak with pockets but those pockets could be hard to get to depending on injury sine I'd have to take the pack off. I will take my chances on a phone bruise in order to have it within reach.
It's funny, a rider who says his jacket armor broke seven of his ribs says you shouldn't have a phone in your jacket because it might injure you; from his example it looks like you shouldn't have armor in your jacket either!
Advanced pancreatic cancer found 04/2010. Have outlived +/- 97% of patients with this diagnosis, but 08/2013 cancer now in liver, vascular system and lungs with 20+ lung tumors. Sick/weak sometimes, not riding much. No more treatments & now under Hospice care.