Hm?
I was actually talking about peak performance in athletes, the differences between men and women. Not mean values.
You know, before power armor gets added on, which makes some of that redundant. And the boltguns, which don't need strength or an extra inch or three of height to use. Or the Predator tanks. Plus, a lot of that difference is actually the result of different metabolic processes, or rather, not different per se, but the way a female human body and a male human body processes stuff, there's more fat on the woman, even at peak performance levels (like 8% versus 4% or something, I'm guessing a decent amount of that is fat around the breasts and hips). With Space Marines, considering they're already being turned into eunuchs or something (I believe I read that their sex drive is reduced significantly), it just doesn't seem like that would remain a factor. Plus, like I said, hormone treatments.
Plus, if Sisters of Battle are getting power armor, then I find it hard to believe it's solely about cost of outfitting and training them. I figure it's a combination of the Emperor being a dude and wanting dude-bros to go crusading with(probably resentful of woman after having watched anyone he ever formed a love life with die as he never aged, and presumably he wasn't gay though I could believe it with those luscious locks), human women being more valuable for making more humans, according to the opinion of some in-universe characters(Krieg, for example, although I question what they do with all the sterile women if they just decide not to have them be soldiers(fuckin' idiots)), and the Emperor had a hard enough time making it work for one gender(besides the whole 'I don't want a race of super soldiers to replace humans' thing), so he probably figured 'eh, good enough, I'm bored, let's go KILL THINGS YEAH!'
...yes I am heretek