They will help to strengthen the chassis, so that stops the suspension from distorting under load therefore helping to keep the wheels on the ground, which leads to better road holding. Down side of rear strut is you might have trouble if you wanted to put 'stuff' in the back with the rear seats down! I have a front upper, lower and rear, I got the no thrills galvinised version think I paid about £50 for the lot from big boys toys.
