On tarmac, a road bike will be significantly faster than a hybrid. This is because the road bike is lighter than a hybrid and has skinnier slicker tyres to reduce rolling resistance. If you ride your road bikes with your hands on the drops (the bottom of the handlebars) you'll also reduce wind resistance and get more power from your legs as your whole body angle changes.
I reckon I usually get about 4-6 mph more from my Bianchi roadbike than my Marin hybrid, but that will differ for each rider, and with the bikes you are comparing.
