Has anybody switched from a j frame to the Glock 43 for conceal carry?
No one gives up a 642 for a G43 with recoil even more snappy.
Cartridge comparisons mean nothing if you can't control it and get on target.
When I ran a 642 I even practiced with one hand and even one hand off-hand. (although the off-hand was a work in progress)

Point is you better be able to fire any gun at least one handed even if it's just your strong hand.
G43 has a stellar reputation already if you lean that way.
I've own myself a couple in the .45 flavor, but that safe action trigger cause malfunctions for me because I could not adapt to it and when you can't trust your carry gun than get the heck away from it as fast as you can.
I can tell you this though, I never could have shot either one with one hand, which is why also besides not trusting them they where never my primary draw.
642 up front was.
And I carried both.
Fast forward, I now carry a Governor and I might be able to shoot the A.C.P or the G.A.P one handed, (haven't practiced for it yet I'm still getting use to it and putting it through it's paces)
But there is no way in heck you are shooting that one handed with .410 bore or .45 LC which is how I keep it loaded, my reloads are the A.C.P. Not to mention I miss and loss my front pocket quick draw.
So guess what, I'm going back to 2 gun carry.
The only way you will ever truly know what works for you is by trial and error. Compromise is in order if you lack the funds or the time and effort, but to much compromise defeats the purpose usually.
Good luck with your choices.