Is the 40 cal flat point FMJ any better at stopping than 9mm or 45ACP roundnose FMJ?
I have no experience with that particular bullet. But my observations with other cartridges is that their is a noticeable difference between a round nose and a flat nose.
Example
I shot a Fox that was trying to get to our chickens with a 9mm FMJ and while it did run away, it seemed somewhat less than impressed. I went out the next day and I never found a dead fox, and the blood trail was small and short (meaning the wound managed to seal.
I've shot coyote's with .38 Special 148 & 158 wadcutters and they give more of a reaction to the hit, and in each case I did find the dead animal.
Flat points just destroy more flesh IME.