Own all 3 and can't really pick a favorite, 56 BTW. The 9mm gets shot more because it is the cheapest, and still effective. 45 is probably the least effective round, and most over rated. But my favorite guns are chambered in 45 so it gets used a lot. I probably like the 40 the least, no history to speak of, but it is the round I'd trust to be the most effective if it had to be used for what it was made for.