There is something to be said for both setups. Slinging it is the safer route because you can detect leaks and keep an eye on the pressure gauge. However, it can get in the way if you are doing photography. On my last underwater photo shoot, my pony bottle killed what would have been the best shot of the whole vacation: I was diving on a North Carolina wreck, trying to get close-up shots of the large Sandtiger sharks that slowly cruised the wreck. I was hovering just above the main deck, positioning myself for an incoming shark, and when he came right toward me, I started to move forward, raised my rig, framed the shark's face in my viewfinder and just when I was about to press the shutter for an awesome portrait, something jerked me back. I thought "FCUK!!!!!", the shark went past me and that was it. Turned out my slung pony had snagged a piece of wreckage and held me back. Boy, was I pissed! At that moment, I swore to back-mount it in the future. However, in the meantime I've come to realize that perhaps I need to practice more and simply get used to diving with the pony and take it into account better. If photography is not an issue for you, then slinging your pony is a no-brainer.