Grip
I don't have a quantitative answer other than grip fit.
I just got back into owning guns this last December. I am up to 3 and my wife is up to one.
This single criteria is the one that matters 1st and most. It isn't getting through the gate if it doesn't feel right.
Now brands, for the most part, do tend towards similar grips, but I don't discount a brand by only a few examples.
Bersa - Love my Thunder 380 and Mini FireStorm 40, absolutely hate the BP9CC
Taurus - hate my son's PT840C, but I like the 24/7, and these are very similar
Colt - like everything I have touched, except the Mustang
Glock - with you there, but I'll find one I like someday
Tanfoglio (EAA) - have yet to find one I don't like except color (they are getting crazy with that part)
As far as my wife..... darned near nothing got through her gate, except my Witness and her DB9. Size got them looked at, grip got them through the gate, able to rack was next, simplicity last. Took 3 months to finally get her one she liked. Darned thing is even referred to as a 'baby Glock', though it isn't near as homely.