love my sig p556 swat. i put a single point sling on it, so i can push it away from my body for stabilization. this is important as you know if you've ever fired an AR pistol before. it just feels awkward without the stock. might be better with a foregrip, but you have to have the aow permit to put one on a pistol. imo, the best accessory for an AR pistol is a good laser.
plus, if you ever decide you want to turn it into an sbr, it's piston drive, so it can be a folding stock.