Personal preference and acclimation plays a big role in choice. I use both styles. IMO, the main differences of the stock design has to do with ergonomics. If you are going to be spending a lot of time shooting in the prone, sttting,kneeling positions, the vertical grip enables a more comfortable elbow down position that results a "straight" wrist position. Maintaining a straight wrist supports accurate shooting and results in greater comfort/less fatigue, along with better control of the rifle in terms of applying rearward pressure from prone or when the elbow is supported by the knee/leg when sitting to kneeling. For the more upright shooting positions tree stand, shooting sticks, off-hand, where the shooter is accustomed to a horizontal elbow, the curved/pistol grip with less angle allows for more comfortable, straighter(wrist/body) shooting position, that tends to be a faster and more natural ergonomically. This is why you see the straight/open grips on the older military designs(ie Garand, Springfield, etc) and the handy lever actions. Of course it can come down to what you are used to. If you spent most of your life shooting an AR15 platform, shooting elbow down, this design may feel more natural to you. I personally can shoot well using either from varied positions.....but....If I'm in the Wyoming foothills hunting deer and antelope I'm more comfortable with my vertical grip where 80% of my shooting is prone, or elbow supported, sitting. Later season hunting in the North woods from stands or blinds, the standard pistol grip feels and handles much better.......IMO.