I had Scattergun Tech ghost rings on my 870P and found they din't work for me. Without good lighting (such as under a canopy of trees), I couldn't center the post in the ring. It mad precision shooting with slugs very difficult in low light (at least for me).
I switched to the standard Remington police rifle sights on my new 870P and they are quick, precise, and quite rugged. With just a dab of orange paint they are very easy to pick up in all reasonable lighting conditions, and very precise for slug shooting. Our department has about a dozen of the 870's equipped with rifle sights and after 15+yrs of being banged around in patrol cars and being shot, not one front sight has come off. Two of the rear leafs (not the welded base, just the screwed-on leaf) have broken off over the years. That's primarily because the locking "clamshell" we use presses the leaf right up against the divider/cage steel frame and as the guns are slammed in the rack a couple of hundred times, the screw breaks.
Also, you can upgrade the rear leaf and front bead to tritium or fiber optic by simply using a drift punch or an allen wrench.
Finally, if you have the ghost rings installed and find you don't like them (as was my case), taking them off will leave holes in the reciever and a big mess on the front of the barrel. With the rifle sights, removing them is an easy barrel swap.