I typically use aluminum 80s and my husband tries to use steel when he can, if we do this, we are pretty close in air consumption by the time we need to ascend. If we are both on alum 80s then I gotta go up when he does, even if i still have 1500psi left (ugh) - but I'm a good buddy :)
I have used steel once and loved it because I didn't need to carry any weight, but at the same time... what would I ditch if I needed too lol