I have the choate adjustable stock on one of my 870's. I keep it at it's shortest length. Speedfeed makes a shorter stock too. I am 5'10" and my arms are average length etc... When you have a shotgun, with extended mag tube, 7 to 8 rounds, side saddle with 6 more rounds and a light, you have a gun that is heavy even if the barrel is only 20" long. If you get your forearm elbow extended too far out, it becomes very hard to support that gun. I like to make a shorter triangle with my elbow at that the downward point.
I also have noticed in recent years possibly some damage in my wrist, shoulder and elbows from recoil and other injuries. Just wear and tear, I turn 40 next week! So my elbow does not like beig extended out as far.
For me in a normal situation, like hunting, I prefer a standard stock, I can shoot either type quickly, but in some ways a standard stock handles better. But for home defense, I find a shorter LOP combined with a pistol grip helps to control the gun better. Again, tucking those elbows in "under" my gun. A shorter LOP moves your trigger hand elbow back too. It also makes 1 handed reloads easier while you keep the gun shouldered. Field guns are carried a lot and shot a little, so they are light weight. Tactical shotguns are heavy, different feel.
Finally, I find with heavy loads, I can keep the gun mounted even tighter on my shoulder when I use a pistol grip. I prefer not to use magnum loads, and I shoot the same way regardless of loads being used, but I have conditioned myself when I pick up a shotgun with a pistol grip, I shoulder it just a little harder and firmer. This always improves accuracy and it helps to reduce fatigue when practicing with it. 25 to 50 rounds of buck and slugs can wear you out!
PS I also believe that the wrist angle involved with a pistol grip is better for holding heavier weight up. It brings your thumb back closer to your wrist, more like holding a 1911 in your hand, lets you lock your wrist. It also rotates your arm more under the stock instead of running along side of it. Remember these opinions are free! But a stock won't cost you that much to experiment with it.