Is there a reason to take the Sororitas career from the Inquisitor's Handbook with the new release of Blood of Martyrs? Seems like the wise choice would be to go with the Battle Sister path. Is there something I'm missing?

A lot of it depends on your GM. Mine has outright banned the BoM version, meaning all that's left is the IH version.

WillisRBC said:

I have used both sources, though mainly BOM and then the free PDF upgrade for Palatines for making an ascended sister to fit into DW. Blood of the martyrs is closer to what a sister is, but IH is more geared to making them equal to the power level of other acolytes in DH. It really depends on your campaign I guess.

Maybe it is possible to rework the IH career into an all-out Novice path. Novices are actually a neat workaround to roleplay Sisterhood characters within the power level of DH without breaking away from the Sororitas fluff.

I think that you can use I.H. SoB for represent Sisters from Orders Magrida and Orders Plansilium (cfr. BoM, p.78)