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What seems plausible though is the physically stronger one is the more apt one would be able to deal with the demands placed on the body.........when you become wore down physically it can be hard to be "tough" mentally regardless of sex.

I look at this a little bit differently. If your talking someone who's fit vs a couch spud then the odds are the fit person will prevail.
Assuming everyone is fit enough to undertake a trip, then the mentally tough will prevail long after the physically stronger but mentally weaker throw in the towel.
Look at the elite Navy Seals. Everyone that enters training is the fittest of the fittest in their respective services. 1 in 100 make it thru the training. The difference is mental toughness, the will to persevere.
Your mind leads, your body follows.

I've taken enough mixed workout classes to know that while women may initially "whine" more than men, once they get their minds "right", they find that their not really the "weaker" sex and guys find out that muscle without resolve doesn't take you very far. ;)