I doubt there will be any resolution to this debate. Anecdotal evidence is a contradiction in terms. There are just too many factors that have to be controlled and I agree with the above comment that there's not much compelling need for someone to design a double blind study with a significant number of divers, diving identical profiles -- all to test something that is very difficult to measure and may have as much to do with how well they slept the night before as what it in their bottle. If the fate of the world depended on it, you could figure it out, but it just isn't that important.
So, I dive nitrox when it is warranted and air when it is not. That decision is based on depth, desired bottom time, and desired conservatism.
Anecdotally (there I go....), and IMHO, adding a hood, vest or an extra mm of neoprene in order to stay a little warmer is going to have far more impact on how you feel after a dive than diving nitrox.
So, I dive nitrox when it is warranted and air when it is not. That decision is based on depth, desired bottom time, and desired conservatism.
Anecdotally (there I go....), and IMHO, adding a hood, vest or an extra mm of neoprene in order to stay a little warmer is going to have far more impact on how you feel after a dive than diving nitrox.