I think it's a little of both. Women do have stronger immune systems in general, meant to help protect their unborn children, shield them from things, but then they also do get some of those immune factors that newborns have back (IGF and even some stem cells, especially from umbilical cord and placenta).
Men in general tend to work more dangerous jobs (accidents), more physical jobs (heart attacks), more stressful jobs (also heart attacks and strokes), and, ironically, also the more sedentary jobs (also heart attacks ... since you sit there in a cube, at a desk, behind a computer for 8 hours per day).
Of course, during war time, the male population can get decimated. I've heard stories about WW2 (in Hungary) from my grandparents, since the men were hauled off to be canon fodder at the tip of the Russian front (as a buffer to protect the Germans), and very few of them returned from many places. There's some prophecy somewhere about a time when ten women will be competing for each man who survived.
But here I think is the ideal prep, in fact, it's nature's prep, or God's prep in a way.
If there's an impending economic collapse, what better way to store preps than to put on like 200 pounds of body weight? That stored body fact could keep you going for a year, and, as you put the weight on, you gradually develop the leg strength to easily carry it. Then, as you drop the weight, you'd have enough muscle to kick butt. And it's about the most efficient storage you can get. PLUS, the government can steal your food preps, but would never think to liposuction you to get rid of those preps. At 3500 calories per pound of body fat, 200 pounds would get you 2,000 calories per day for an entire year. So you get a year's supply of food that you can carry around with you. Can you imagine carrying a year's supply of storable food with you? You couldn't. Your body keeps it from spoiling (no refrigeration or freeze drying or anything else required).