There is one other big advantage for steel tanks over aluminum....longevity. I’ve only been diving 4 years, but have had to turn in two aluminum tanks for scrap metal. From what I am being told by the people who failed my tanks at hydro, many dive shops are refusing to even fill aluminum tanks made before 1990 any more. Apparently there have been a few too many accidents? But I have a Steel 72 tank from 30 years ago that keep going and going and going.... And now I own four Steel 100’s because it seems like a safe investment.