Most would say that the Discreet Carry Concept clip (they make the metal clips for Tenicor specifically) are the best there is out there for holsters. I would have to agree as they are very reliable. Highly unlikely that the holster would ever be ripped away from you in a hand to hand struggle, come out with your gun when drawing, clips snap in half or crack, etc.. I particularly like the DCC design, but also have other DCC clips on other non-Tenicor products. They are indeed a PITA at first, but over time have set in or I simply found an easy way to don on and off now.
I have found that partially installing one clip, then the other, and repeating until they click in place to be the easiest while the gun is in the holster for me to put on. Pulling the metal tabs with your pointer fingers and thumbs resting on the top most part of the clips simultaneously works the best to take off, again while the gun is in the holster and then slipping upwards off the belt.
If wearing a duty belt, it sounds like you carry a gun for a living, I would say give the DCC metal clips more of a shot, as they will be more reliable than any plastic clip that can break, crack, or flex enough to not be secure anymore. The metal Ulti-clips look pretty solid, but I have never had the need to try them. They do look a bit more complex/have smaller moving parts (the hinge?) as to how they work so maybe keep that in mind too in your decision!