The 1.8 has 13bhp difference from factory, but the 1.6 has a shorter gear ratio i believe making it quicker of the mark.. there are other factors such as weight, wheel size and engine condition load of factors.. mkI\mkII both had different engines due to changes on the head\throttle body\sensors\manifold..
My 1.8 went like sh*t off a stick, that much so the HGT 155 i had felt slow sometimes....