I've indulged in so many arguments over the years, both for and against JtR being a woman... I like to argue all sides of an idea, it gives me perspective.
One hand, yes a woman can be strong, and a woman can be very murderous. A woman can even be crazy-*advertiser censored* enough to want to eviscerate her victims and spend time draping their intestines around the victim's neck - or in Mary Kelly's case, flaying the meat off her bones, as well... and leaving it, with her internal organs, on a bedside table... Sure, a woman could have done that.
But statistically, very very few women are on record for even a single exampleof even the ballpark level of this type of murder. In fact, I don't think I can find ONE. Let alone a series of murders of the same ilk.
In the "for" basket goes the fact that the killer likely did not have penile rape on his/her mind, being that between the actual killing and the subsequent mutilation, there was not a lot of time -- the mutilation itself was probably the primary goal. Also, there's good evidence that the victims were likely brought down fast, silenced/killed via strangulation/cut throats -- and very possibly from behind. While a lot of street prostitutes probably offered themselves from behind, leaning against a wall (the streets were *filthy* and they had those big skirts on, big doubts they ever lay down for sex in all the muck) there's also a chance they were simply blitz-attacked from behind, rapidly and thus little actual strength was needed.
I do tend to think the killer was a man, however I'd not fall off my chair if it turned out to be a woman after all.