There is a difference; the "Duty" is the first Gen of this model, quickly identified by a round ring hammer. The 2nd Gen P-07 has sculpted top edges of the slide on the muzzle end with front cocking serrations, and also having an angular / flat top hammer. I believe there were other changes as well, I'm sure someone else can add more info.
The Duty had 16 + 1 capacity, while the newer version is 15 + 1. The new P-07 has a newly-designed trigger and hammer. The finish on the slide and barrel have also been upgraded. It also has steel three-dot sights as opposed to the U-notch on the Duty.
It's just an overall better gun than the original Duty.