In a plastic frame gun, I've found the .40's recoil more than the .45's because the .40's are in smaller frame guns. And the .40's tend to not hold up well, where the .45's do.
I watched a 40 Glock whip a big burly SRT type's azz for three days on a Roger's Range. They gave him a 9mm Glock and he started hitting plates.
This plus one. My Kahr CW40 blew itself apart with less than 500rounds through it.
Good buddy told me to never bring a 9 to a 44mag fight. I said why you couldn't hit me with that 44 anyway. Then he shot my 9. Doubt he'll say that again.
