While I prefer the bigger bore handguns, (with the loads we have today) there's not much 'wrong' with a 9mm. While a .40 might be 'better', and some might think a .357 Sig is the stuff, a 9mm can
do it just as well, with modern HPs. I think a .45 is the epitome of a defensive handgun round, but it doesn't mean a 9mm won't fit the bill, either. BTW, I do
own a Glock 20 10mm. It and the 21 are just about the only Glocks that come close to feeling right in my hand. The 1911s, XDs, Sigs, etc. ALL have better ergonomics, IMO, and (while I like my Glock) I don't think a Glock is a Sig or custom 1911....JMO. Now, there are some factory 10mm loads that are hot/full power, but they are few and far between. Also, Glock barrels won't like the cast loads available for hunting, so an aftermarket bbl would be in oder. The purpose of my Glock 20 is for trail/hunting/truck/home defense...not constant concealed carry. The 10mm has a unique ability with it's loads to be switched out for defense loads vs hunting loads, and it can shoot hogs just as easily as it can shoot democrats.
Cartridges/platforms will always be debatable, because it's more need/intended use, feel, and personal preference, which is why there is so much out there. On a side not, full house 10mm loads from the full-sized Glock are easier to handle than .40 cal loads out of a Glock 27. My 9yr-old loves shooting my Glock 20 with Cor Bon DPX loads, and he can hit AND hang onto it. Just go shoot stuff. The way something shoots, carries, costs, and feels, determines more of my purchase than caliber, generally.
Here's a thought: Let the ducks work and decoy.