I'm not a decompression diver and I have no opinion about which is the superior mix. However, I do understand something about the underlying mathematics of the decompression calculations. There is typically too much hand waving in the discussions. It is not sufficient to simply say one mix has a higher partial pressure so it is obviously superior. The dynamics of off-gassing are important and must not be ignored. 80/20 allows you to go to a higher partial pressure earlier. You are at a lower partial pressure at 20 and perhaps 10 ft, but on 100% O2 there air breaks are required which tend to offset O2's partial pressure advantage.
Therefore, the optimum solution in terms of deco time is not immediately obvious, you must calculate the decompression schedule and determine which mix is delivers shorter hang times. The risk of oxtox should of course be balanced with accelerated deco times. It would be unwise for example to reduce hang times by say 3 minutes if the risk of oxtox was doubled.
Of course other anecdotally reported benefits such as feeling better with a specific mix are difficult to quantify and if true indicate the models need further refinement.
Ralph
