My instructor claimed that women are better suited by nature to shoot well. Their center of balance is lower so they've got a better platform to start with.
I'm an instructor as well (that an $5 will get you coffee at Starbucks); I've heard this many times [center of gravity is lower and therefore a better shooting platform] and I think that this is bass ackwards. True for many other things (most evident on the uneven parallel bars), but not actually shooting.
All things being equal (weight specifically) the higher your center of gravity is the more you're able to "soak up" recoil and get back on target faster. "High mass" helps, "low mass" has no effect.
That said, typically women are better shooters than men, not because they have a lower center of mass (which in MHO works against them), but because the possessors of the Y chromosome think that all gun knowledge is contained within that chromosome and just flat out don't listen to anyone.
I have lost track of how many times the following scenario has played out in class:
1) Husband cajoles wife into taking class, one of the bargaining points is that he'll take the class with her.
2) We separate the two to get rid of the husband-wife dynamics.
3) Wife listens to class, faithfully follows lessons and is receptive to coaching.
4) Husband, because all knowledge is contained in his Y chromosome, is bored to tears and doesn't pay attention. Typically needs to be reminded about basic safety again and again as he sweeps other in the class multiple times, leaves his finger on the trigger, etc. This constant reminding typically annoys him because he knows so much more about shooting than the instructors.
5) Range day. We put the husband and wife next to each other on the shooting line.
6) Wife kicks the husband's arse. Except in a few cases* not by just a little, but by a lot. This is why we put them side by side. This delights the wife, sparking an interest in shooting!
7) NOW the husband starts to listen. In a compressed amount of time we have to go over everything he didn't pay attention to in class.
8) Husband improves, but typically not to the extent that he could have.
If I had a nickel...
O2
* Sometimes we do get husbands that are very good shooters that the wife doesn't have chance to better. Typically this is because they denied their Y chromosome sometime in the past and actually paid attention to previous training (and the training was good). Despite already being good shooters that attitude still prevails and they pay attention in class and almost always pick up something new. We can detect the attitude difference within minutes at the start of a class.