I know you said 9mm+ but don't forget the .380 ACP.
.380 and "duty weapon" should not be in the same sentence.
OP, you are not going to find a softer shooting, duty caliber then the 9mm. It sounds like you need a training course and alot more time on the range to build up endurance. The Glock 19 would be a fine choice or the full-size G17. The S&W M&P would also be a good choice. These two guns make up a large percentage of LEO duty weapons. The Walther PPQ would be another gun similar to the Glock and S&W; the PPQ's are well known for their excellent out of the box trigger. The Sig 226 and 229 are also widely used but the DA/SA is not as simplistic as a striker fired type guns DAO (Glock/S&W). Sig has their DAK style trigger but I've never been too fond of it; you would have to try it for yourself and make your own determination. The Beretta 92 is another good gun but has a DA/SA type trigger and controls that are not as simplistic as the Glock or S&W. Personally, I'd stay away from the XD line for a service weapon due to the need to depress the grip safety to rack the slide. That is a no go for me.
Good luck with your choice and above all get training and shoot the crap out of it when you get it. A second identical gun would be a wise purchase for use as a training gun and a backup gun incase your duty gun needs work and is put out of service. Two is one, one is none.