The three projects, at least at this stage, don't have the same scope. The S&P proposal really only addresses the Faculty of Law, while KPMB fully works out what to do with the Faculty of Music too, and throws in a Biggish Dig solution to the vehicular and parking problem in the whole precinct.
I suspect that Music, stuck for decades behind Falconer and the planetarium, and with ROM's driveway for a sidewalk, is going to like what is sees, which is an atrium, a real front door, and finally some presence, and will start lobbying in that direction.
What I suspect (maybe incorrectly) not many at either faculty will like is Saucier & Perrotte. It's bold and interesting architecture, but I'm not sure I'd wish it into existence to loom over Philosopher's Walk, and I'm fairly sure it would be a tough sell.
KPMB is conservative. What they do they typically do very well, but it's not to view their treatment of the curving flank along Queen's Park with disappointment. Maybe the Law mavens could throw down the gauntlent and demand they draw something that isn't a right angle.