I have both a full-size M&P .40 and a Shield .40, and I honestly do not feel any difference in recoil between them. I also have 9mm factory barrels for both and have hundreds of rounds of 9mm downrange. I find that, at age 65, I tire quicker shooting .40 than I do with 9mm. So, if I have a class that will require 200-300 rounds, I use my 9mm barrels and magazines. And I must note, I have not experienced misfeeds or jamming with either pistol with .40 or 9mm. For me, it's a "comfort thing". A long class, or an extended range session is simply more comfortable with 9mm. Oh yeah! It's cheaper, too, and that helps me go more often.
I almost forgot to add; for home defense, and for carry, I use Corbon PowrBall .40 or Double Tap .40 HP's.
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