I am based in Toronto and happen to know MBA grads from Ivey/Rotman/Queens.
LBS is the hands-down winner if you're looking for a brand leader and international exposure. But I think it's important to consider where you want to work post-grad - if it is in Canada, than an MBA from LBS (or any other school not named H/S/W) will not be viewed much differently than one from Rotman/Ivey and will have a longer return on investment due to higher costs. You'll also have a much tougher time working the Canadian job market from across the pond, and will likely need to rely on your own network. IMHO, 5 years down the road, recruiters will be far more interested in what you've done in your post-MBA career than what school you attended. And if you pursue the entrepreneurship route, you'll want your contacts to be established in the region where you plan on doing business (and not just names out of an alumni phonebook).
I think the reputations of Rotman/Ivey are misleading - Rotman is much more than just a "Finance" school and does well in many other sectors, just as Ivey grads can excel in Finance and not just as MCs. In the end, it's a wash. 90+% case (Ivey) vs. 60/40% lecture/case is a personal preference based on your learning style. Keep in mind that Rotman also has the Intergrative Management Curriculum in 2nd year which is much more interactive than any case study could be. Personally, I think Dean Martin has done an incredible job with Rotman since joining in 1998, and it continues to innovate and improve in the rankings, while Ivey remains rather stagnant. I would not be surprised if Rotman becomes an elite school in the next 7 - 10 years. And that's why I chose it.