I've shot both the PM9 and the 642.
What you will notice first when firing each one is "Wow... this gun is SNAPPY".
The second thing you will notice is whether or not you hit paper with any of your rounds
After 5 shots out of the 642 (or any J Frame) my first thought is always "F... this gun is snappy." Then I look at my target and say... "Eh... 2 out of 5 on paper @ 21 feet ain't bad." [sad2]
After 6/7 shots out of the PM9 my first thought was "F... this gun is snappy." Then I look at my target and see that all rounds are on paper... making roughly a 6 inch group at 21 feet.
So FOR ME... both are snappy as balls... but if I were to have to use either one in a defensive situation... I know I can put rounds on target with the PM9. Not so much with the 642.
Like everyone has suggested... it's best to have her try both out.
PaulD was generous enough to let me try out his PM9. Shoot him a PM and I'm sure he'd be glad to let you and the Mrs. try it out at Mass Rifle Association or Harvard Sportsman Club (which I believe he's switching to next month?).
And Paul, since I'm "volunteering" your PM9 I'd be glad to meet you guys at the range, hang out... and clean the PM9 afterward for you
I just saw this post but I'm happy to let anyone try out the PM9 and yes, I'm done at MRA.
Also, Hanwei, you can try my AR and clean that afterwards too.