Keesje, if airlines made decisions based on purely range V payload charts, then everyone would be doing it. Bear in mind they are going to be taking the Max 8, and not the 900.
In the missions that Air Canada will typically use their 737's for will allow for shorter turn times, higher utilisation, and greater revenue.
Air Canada are facing up to the reality that they need an airframe to replace their ageing 320/321's...and in most aspects the max in their configuration will prove to be superior to the NEO.