Hi,
I have done the Winnipeg to Toronto drive and it's LONG. We drove through Chicago and Detroit on the way there and through Canada on the way back.
We hit traffic around Chicago which definitely seemed to add some time to our trip, but in theory this is supposed to be the shorter way. So if you can take into account, to not hit a rush hour, that would probably be ideal. The roads are great with lots of rest stops.
The recommended trip through Canada is believe it or not, the 11 because of all the twists and turns which add to the amount of time the 17 would take. The 11 also takes you through some beautiful country. Winter driving would be slightly terrifying though, so this depends on when you plan to do this. Gas stations also start to get few and far between eventually to, so you want to make sure to fill up when you have the chance.
You can double check with some people, but I was told by people who drove each route many times, that it's faster than the 17, although the 17 runs along the Great Lakes and is probably also very scenic.
Either way it's still a bit of a drive. It took us about 30 hours I believe on the way there. So keep that in mind.
Good luck and maybe you should take me to Toronto with you. I'm overdue for a visit. 
Cheers,
Amie