Without knowing it, the conversation is balancing between two shooting stance principles. The M14 was designed to be fired from the shoulder with the cheek on the stock, the eye aligned to the backsight, the supporting hand on the forestock and a sling under the wrist. The soldier was trained in marksmanship and probably only wore a combat shirt. The M4 carbine, which the OP is dancing towards, was designed to be fired from a more squared body position. The butt is on the chest, closer to the centreline. The firer has likely collapsed the butt and is wearing body armour. The rifle probably has an optical sight. The shooter has two eyes open. The squared body means the supporting arm is not as far forward as the firing hand.
If the OP wants to emulate a 20th century combat soldier's stance, go ahead. If he wants to shoot with a sling, then a foreward grip is less convenient. If he wants to shoot single shots off a bag from a bench, then a grip will get in the way.