Exactly, because the small cross sectional area of the smaller syringe is exerting more pressure (eg. 13mm master piston on an RB lever instead of 14mm on HS33... similarly, increasing slave system diameter has the same effect). So, the brake isn't '25% stronger', but the system is easily capable of offering 25% more mechanical advantage by simply increasing the diameter of the slave pistons.... downsides, as Bigman said, are spongy lever feeling and having to set the cylinders/pads closer.