Mr. Ingels tends to stir strong emotions. In the six years since he founded the Bjarke Ingels Group (BIG) in Copenhagen, he has become sought after by public and private clients throughout Europe, in the U.S. and now Canada. (A few weeks from now, Mr. Gillespie will unwrap a BIG development that he and his business partners intend to put up in the Toronto suburb of Don Mills.) He has earned renown as a superb communicator and a strong thinker about what makes cities successful, but also as a practical architect keenly attuned to the specific problems that come with each job.