I used to drive between Ottawa and Toronto many times a year and I encountered conditions from freezing rain to heavy snow on 401, so I guess I can provide you some good advices.
Even you're on major highway, snow could come any time during your trip. You may end up driving in snow before the snow removal crew arrive. I highly recommend using winter tires. Another thing no one mentioned is that you should carry enough windshield fluid. Fill it up before you leave. It will be very useful for maintaining a clear sight. Heavy fog may appear on 416 under certain condition, which may be dangerous. In this case, drive with extreme caution because multiple car pile-up occured before when fog mixed with black ice on 416. Fill up your tank at Port Hope on 401E, it's much cheaper than Toronto. On your way back, fill up in Ottawa and again at Port Hope on 401W.
I have been traveling every week to and fro Ottawa and Toronto since 2000.
Besides the above, I want to add my 2 cents :
1. Car tune up before winter (CHECK car battery, wiper blade, spark plug, brake. Change engine oil to 5W30)
2. Windshield fluid better with de-icer
3. A shovel
4. Chocolate bar (energy...), hot drink, blanket
5. Member of any CAA/Canadian Tire Club ... (just in case you need road side assistance)
6. Cell phone fully charged
7. Defensive instead of aggressive (Slow is better than fast)
I have seen a lot of super cars (Jeep, TRUCKS, SUV) ended up in the ditch.
Snow Tire, AWD, ABS, etc are all useless if there is BLACK Ice.
The worse case scenario your may encounter is WHITE OUT, visibility can be as low as 50 meters, keep your car speed slow and make sure you have enough distance between your car and the car in front. If panic, turn on HAZARD light. Also, be patience, don't make unnecessary lane change (usually black ice accumulated between lanes).
It is better LATE than never...
Again, my 2 cents
Good luck