My brother was a cop for 2 yrs and he was out shooting with his captain and he accidentally grabbed his 40 S&W instead of his 45ACP,it did shoot but not eject right. In fact he fired 3 or 4 shots thru his Kimber before his realized it was an ammo problem and not the gun.
That being said, I think the 45 is easier to shoot than the 40. I think both are deadly rounds and you might get a little more range from the 40, if you shoot either a lot you can be deadly from any range.
Remember the battle of Athens, TN!
"Work as if you were to live 100 Years, Pray as if you were to die To-morrow." --Benjamin Franklin