Take this for what it is. I just watched a utube vedio about the FBI changing to the new 9mm. Some agents could not handle the 40S&W , cost of ammo and wear on guns was stated as reasons for the switch. I really don't see a problem . I also don't see a reason to give up a 40 S&W if you own one and can shoot it well.
With all the 40 S&W Glocks trade ins on the market at low prices it might be the best time to get one
Then get the 9mm conversion barrel for it . The pratice with 9 mm and carry 40 S&W.