Since I'm looking at picking up one or two police trade in .40 Glocks for reasons, I'll chime in.
Personally, other than incorporated as part of my I'm bored, and want to fuck with something else to remind me why I'm shooting a 9mm that I have various addons on, I don't really think there is a whole lot of benefit. I personally, don't think there are much in the way of benefits for added recoil in training. There is also the whole thing with .40S&W is more expensive than 9mm, so it a thing there. More so with .40 locally being only like a $1 or two cheaper than .45acp, and in a few instances recently it was actually more, which made me scratch my head, though I was gobbling up that .45acp to feed my 1911.
Only real reasons I can come up with my want for a Glock 22 and 23 are as more or less stock play things, because I want more guns(which is either a great or shitty reason depending on the person), and because I can add a couple hundo cash and grab extra caliber swap barrels for more over priced odd ball rounds to play with. I suppose I could justify the 22 as pistol for a full caliber conversion for competition since it would be a little bit heavier than my 17.
My end point, no reason to not buy if you want them. But, for training I think it dubious. And I say that while looking at grabbing two. So....