All cyclists have different proportions and are of different sizes. It is very difficult to tell what size bike is best for any rider without giving it a try.
If you haven't yet, check out our sizing charts here: http://www.norco.com/sizing/
While our charts may help you narrow down your size, the best bet for ensuring that a bike fits properly is to work with your local bicycle retailer. Bicycle retailers are trained in fitting a bike properly and making sure that you have the best cycling experience possible.