I'd get the 45 myself and seek a K9 or an MK9 for the all steel Cadillac of Kahrs.
I have a K40 and just don't care for the flip. It isn't painful and I can shoot it all day but it takes awhile to get back on target following each shot.
On the plus side, when all other calibers dry up for whatever reason (usually politics), there's usually still 40 on the shelf. Main reason I keep mine.
I have a K9 that I haven't shot much held in reserve for when the hands/wrists balk at the 45 but so far no issues. Even then I'd probably practice with the 9 and carry my 1911 or PM45.
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."