UCL (University College London - UK) vs UofT (University of Toronto - Canada)

I am trying to choose between these two universities and I really need some insights.

I was accepted in Mechanical Engineering in UCL and from Rotman Commerce in UofT (I plan to take minor in computer science)

Which one is better, both to live and to study? Since I am an international student the price would come close but since London is more expensive to live it will be financially harder, but I can manage that.

Those are very different subjects - which do you really want to study? What are your career plans?