The Comet nose in wind tunnel testing was proven to be the optimum shape for aerodynamic efficiency and cockpit airflow noise reduction, therefore the C Series was designed with that in mind.
However, there are other considerations, mainly structural aspects to keep in mind as well. So a structral smooth design with a blunt, non load-carrying radome attached may be much wiser than a design smooth on the outside but with a significant angle between the windows / center post and the forward pressure bulkhead. There is a good reason behind the (ugly) noses we see on some A and B products...