If you notice the Army/Marines/Swat/Sar/PJ's/seals, etc.. pretty much all use 870 and Benelli's with speed feed type stocks with shortened pull(mostly because they wear armor).
And there is your difference. Short LOP and pistol grips have come about for a specialized CQB role while wearing bulky armor. For general defensive purposes the standard stock works better for most people. Again, reducing LOP often helps, going with a pistol grip rarely helps. The many operators I've worked with tend to have standard style stocks on their personal fighting shotguns.