It's been years since I attended the North American event at Spruce Meadows. I was amazed at the lack of serious crowds at this event. We went early, and parking was excellent. The weather was cloudy, but otherwise fine, and not too hot.
If you can only go to one day of Spruce Meadows, pick a day when you can go see a derby. The derby was incredible, such a long course, with lots of speed and challenging obstacles.