Everybody knows what that means. You need to look at the DIR approach as the big picture, not just at how trim the wings are.
1) The inflator hose is short, just long enough to reach your dry suit inflator and your mouth. Why does it need to be any longer?
2) There is no pull dump valve on the shoulder, this is a failure point and is not needed. Also the area where the valve would be is reinforced and a solid elbow is in its place.
3) The inflator itself is different, it is a low flow inflator, unlike the DR & OMS which are high flow. This means in an equipment failure if the inflator fails it will not fill your wings up so fast that you cannot dump them with the bottom dump valve.
4) Why on earth does anybody need 100lbs of lift, we're not raising the Hunley.
5) If your gear is configured properly, that is, your wings are reinforced, you are not diving with steel tanks with a wetsuit or steel stages you don't need all that lift. If you are using your BC to get to the surface, this is an accident waiting to happen.
6) Cost of double bladders, this doesn't need explanination.
7) A B/P harness is much more secure than any soft body harness.
You can't just pick a part of the DIR system and use it or pick it apart, you have to look at the entire system.
I must admit that my DIR experience is limited, but I can see the advantages to it once I looked at the system as a whole.
ID