There's a very powerful argument, IMO, on the Adepta Sororitas that, unlike the Space Marines being 'dehumanised' and 'programmed', the Sororitas are being...ultra-humanised, distilled.
The Sororitas have their humanity focussed and honed. They've got hate, they've got understanding and comprehension. Where the Iron Hands hate humanity for being weak, the Sororitas would do so because they're ultimately the same as the thing they hate. Their faith, devotion, hope, hatred, aspiration and ambition is all cultivated and pushed towards their near-military (or just military, in the case of Battle Sistsers) discipline.
It's something that's been slightly weakly done, IMO, with the renditions of the Hospitallers. Or perhaps isn't done so well for the 'fiction Sororitas' as opposed to the 'concept Sororitas'. They're certainly similar to the Space Marines, but they're remarkably different too. They're a different breed of dehumanised human. Well, one's a dehumanised human, the other's a dehumanised post-human.
That said, as 'character studies' go, I think they certainly fulfil a similar role and potential in the background, though there's also some lovely nuance to them that distinguishes them from being 'merely' (not that anyone's saying that) female versions of the male role held by Space Marine.