The benefit from deleting the balance shafts aren't entirely based on HP. The shafts are hefty chunks of metal that create parasitic loss of torque and engine response. Due to them also rotating at double the speeds of the crank they can cause catastrophic damage from wear (plenty of guys will tell you about the shafts destroying themselves, bearings and the subsequent loss of oil pressure as a result). You can make useable gains from deleting the balance shafts and the clutch driven cooling fan (throttle response and fuel economy) and both of these mods have an impact on engine wear by reducing loads.