Split finger — index above the nock, middle and ring below — is the classic hunting grip. It balances string pressure across three fingers, tolerates a low nocking point, and keeps the arrow a little farther below your eye, which produces forgiving trajectory and strong instinctive alignment for many shooters.
Three-under puts all three fingers below the nock. The arrow rises toward your eye, point-on distance stretches out, and your gap table compresses — many gap shooters pick up a flatter sight picture immediately. The costs: more finger pinch on the nock if your nocking point is set wrong, and a release that must be cleaner because all the string pressure sits on one side of the arrow.
Try each for a month, not an afternoon. Judge by your groups at 15 and 20 yards from hunting positions, and by whether your nock pinch causes arrows to lift off the rest. Then commit — switching grips mid-season is rebuilding your aiming system from zero.