The path to IOC v. Ranger School for Women Service Members has been significantly different.
They were still doing this at 1AD when I was there, women volunteers were OPCONNED to the Divisional Pre-Ranger course for a period of two months before going through division pre-ranger. Then went through Pre-Ranger at Bliss. Following completion of that they had a recovery period and went to Warrior Training Center at Ft Benning and went through the National Guard's Pre-Ranger course. If they passed that, they returned to Home-Station for Recovery for roughly one-month to six-weeks and then classed up to Ranger School at Ft Benning. Previous to the establishment of the 1AD Pre-Ranger course, they had a TACON attachment to DIV HQ where the women Volunteers spent 4+ months away from their units. The training path for any male Soldier at 1AD was pretty much a solo event until he went through DIV Pre-Ranger.
Mind,Marine IOC was open to women volunteers well before Ranger School was. The course was changed, likely to allow women to complete the course (or so it was said). This is opinion, but it's in this thread. You could say that Standards across the board were basically lowered. The Endurance Course-12 Hour Endurance Run and Obstacle Course previously was an entrance requirement to Marine IOC. Unlike ABOLC or IBOLC for the Army, there is no in-processing on Day 1 because Marines selected for IOC following TBS class up into IOC Prep. Basically a period of getting super fucking fit so that they can sustain the chronic load that IOC puts on Marines. The E-Course ate up Male Marine Officers, I think the figure was previously like 15-20% of an IOC class would get a new MOS following the the failure of the E-Course. Well, now the E-Course is no longer a pass/fail requirement. There were a few women to pass the E-Course before they changed this requirement. However, those that did usually had to physically withdraw because IOC is tough and it was breaking their bodies down. IOC today is still extremely tough course and the numbers show it.
They are different courses (both hard as shit), but the prep periods seem to be completely different approaches.
Another course to look at that's been open a long time and few British Women Soldiers and Marines have passed over time is the Royal Marine Commando Course. The data on this stuff is pretty succinct. The ROI isn't really there, but if you took the Marine or British path, I don't think you're investing that much extra time or money. But the Army's approach has pulled Women Officers and Senior NCOs away from their units for significantly longer periods than is expected of their male counterparts.