Something that I had noticed while working boats over the years, while in school, was that, for a sport that required some strenuous activity and, at the very least, some upper body strength, scuba also seems to attract some of the least physically fit people of most any popular pursuit that I have ever seen; and it was not uncommon to see divers sporting thirty-plus pound weight-belts; a fair share of highly-custom suits; an all-too common incapability of standing from a bench seat while fitted with gear; and we had clear instructions to keep a close eye on each of them.
Almost to a one, those who claimed the greatest benefit from nitrox use, usually fell into that large and in charge category; and perhaps there was something to said for that, in terms of a potential benefit?
I have personally used nitrox since it first became widely available, back in the early 1990s, and had noticed little to no discernible difference between EAN use and that of air -- and typically only use it, nowadays, while spending the lion's share of time below 20-30 meters, but find it an utter waste on shallow repetitive dives.
More often than not, I still mostly dive with air, in Northern California, where it is quite easy to find yourself well below nitrox depths . . .