Winnipeg is colder than Ottawa. I was there in winter 1995-1996. I remembered that in Jan. 1996, for about a week, it was colder than -40 degrees. One day with windchill, it was -55 degrees. The tires became so hard under that temperature, as hard as rocks. People could be frozen to death to walk outside in those days.
Winnipeg is colder in terms of temperature and windchill factor than Ottawa. However, it's more humid here in Ottawa so you would feel colder.
City of Ottawa does not clean snow in all streets, only the major roads and expressways. If you are worried about elderly walking outside on the streets during winter time, Ottawa is not the place to be. There is simply too much snow on the sidewalks through out winter and it's too icy and slippery.