I don't think IB's hire from Gies really or Roman really either. I am not sure how strong or substantial Canadian IB sector is so perhaps I should not be judging it but I may anyway

My guess is you need to do some research about what career paths are actually open to you and are logical after graduation. It is great have dreams and goals that are aimed high.
I think going into MSF, you are going to find yourself with 10-year younger class that will be recruiting into more junior positions and will give you few opportunities to be desired. Rotman may be a better overall fit if you have strong work experience with brands - that's all that matters in Canada is that you have strong brands on your resume and the school does not really drive that much of an advantage.
P.s. not sure if you have a strong preference for countries. Obviously going to Rotman puts you into Canada and Gies into US and you can't really go from Rotman into the US market unless you have a green card or you are a US Citizen.