Anyone who logs onto a tek diving chat room or bulletin board will eventually run into the long hose/short hose debate. On most technical dives with backmount doubles, standard equipment includes one regulator with a normal second stage hose; the other with a seven foot hose for air sharing. The debate centers on whether you should breathe from the long hose, handing it off to your teammate and switching to the short hose in an out-of-air emergency or whether you should breathe from the short hose and hand off the long hose.
Typical long hose breathing configuration secures the short hose second stage on a "necklace" centered high on your chest. The long hose comes under your right arm, diagonally across your chest, then around your neck into your mouth. Typical short hose configuration secures the long hose in bungees or inner tubing along the sides of cylinders or attached to the BC so it pulls free easily in an emergency. The diver breathes from the short hose just as one would while recreational diving.
Proponents of either method can be vehement about their beliefs, with passions strong and opinions loud. Just discussing this issue objectively may offend some people, because I don't express their views. Sorry.
No Clear Advantage
While hose choice has advantages and disadvantages, no one way is right and the other wrong. There are those who adamantly argue to the contrary but no hard facts support either side. People are not getting hurt nor even having close calls because they chose one or the other method. Proponents on both sides cite minor incidents, but the bottom line is there is no quantifiable, hard data pointing to either. It's all speculation.
Issues that Aren't
Proponents of each side put forth arguments supporting their views. Several of these arguments don't hold water.
The out-of-air diver may snatch the regulator out of your mouth. So, say long hose proponents, you should breathe from the second stage you're going to give away. The problem with this argument is that we're talking about tek diving, not recreational diving. In technical diving, divers should have self-control under stress, so having the second stage snatched from your mouth shouldn't be an issue. If it is, perhaps you're diving with people who aren't ready for tek diving. Having to switch regulators adds a major task load to a stressful situation. Short hosers make this claim, but switching should be no big deal. If it is, then maybe you aren't ready for tek diving.
Both sides claim the long hose won't deploy properly the other way. Both are wrong. With proper rigging/routing, the long hose deploys reliably either way.
Pros and Cons
When you look at the issue objectively, both methods have upsides and downsides.
Breathing long hose: This has the edge in streamlining and rigging simplicity. You don't have to stow the hose, which is a plus when you conduct an air sharing drill beforehand (common practice in cave diving). Perhaps the biggest drawback to breathing long hose is that it may conflict with established recreational diving habits. For many good reasons, most recreational divers breathe short hose. In this case, you must learn to switch your air sharing responses when tek diving.
Breathing short hose: Perhaps the biggest advantage is that hose routing feels familiar, which may be one reason new technical divers seem to prefer this setup. Properly stowed, the long hose is out of sight and out of mind until needed. But, you usually can't stow the long hose once you're geared up, so if you deploy it, you either have to get out of the water to restow or get your buddy to do it. Typically you can't see the hose and it may not end up restowed properly. Breathing short hose sacrifices some control of your rigging.
Team diving: There may be a marked safety advantage for one method or the other in team diving, such as on projects. Unified procedures reduce emergency response time by eliminating variables-a possible issue when divers mix and match into different teams at different times. But the benefit comes from everyone using the same method-which isn't the issue.
Sometimes people ask my preference. I used to breathe short hose, but now I breathe long hose (when tek diving). I switched for the logistical, rigging and streamlining advantages. I don't feel I'm safer or less safe than before, nor that I was doing it wrong and now do it right. I just traded one set of pros and cons for another.