Drive defensively & cautiously when driving in Canadian winter + always install snow tires, particularly with RWDs.
For a number of years, I drove with all weather tires all the time because I didn't want to make the investment of an extra set of tires & rims, even visiting Winter Ottawa with them. Finally, I decided not to push my luck too far.
M5 is more glamorous, has higher straight line speed at the end of the track; M4 is lighter, more agile, limbo, makes up all lost grounds on twists and turns.