I got and still have a K40 first. Have since shot a couple K9's and now have one of my own. I much prefer the 9 although I'm a devout 45 fan and carry my PM45 over either.
While not uncomfortable I didn't like the muzzle flip of the 40. I had mine magnaported in hopes it would help and it did to a point but not enough, just too much flip for any kind of follow up shot.
For some it doesn't bother them at all and they love them. I can shoot mine all day but it's not in the rotation for carry.
I've never shot a PM40 but I gotta believe it's got a ton of flip to it being so much lighter.
In Memory of Paul "Dietrich" Stines.
Dad: Say something nice to your cousin Shirley
Dietrich: For a fat girl you sure don't sweat much.
Cue sound of Head slap.
RIP Muggsy & TMan
"If you are a warrior legally authorized to carry a weapon and you step outside without that weapon, then you become a sheep, pretending that JOCKO will not come today."