NY, Boston, and most major cities (I think) only have one marathon. Why should Toronto have 2?
Relevant question, especially since both happen to be within a few weeks of each other.
What is now Goodlife marathon has existed in one form or another for a couple of decades (previously Wang marathon, Shoppers Drug Mart marathon) and used to have a May date. Mid-90s when Shoppers pulled their sponsorship, it closed up shop but re-appeared as Canadian International Marathon, a fall date and less interest in elite level competition.
Waterfront marathon used to be just a half-marathon to wrap up the Coors Light Runner's Choice race series (then Great Canadian Bagel, and now Canada Running Series).
The half was truly a top level event with many Olympic medalists competing over the years. Race director Alan Brookes always has bigger dreams and decided to go head-to-head with CIM and added a marathon to his event. (Now both include a 5km, half and full marathons.)
Brookes has pushed more and more each year to make his event bigger, better and more elite. With more money has come faster runners and this year saw the fastest marathon ever run on Canadian soil.
Theoretically one would think there isn't room on the Toronto race calendar for two marathons, but so far each has managed to draw thousands of participants, indicating that the demand is there. (It's worth noting though that a large percentage take part in the 5km or half-marathon events even though the full is the one with the attention and publicity.)
Presumably if one or the other falters and starts taking a financial or numbers hit, it will succumb or move to a spring date (in fact mayor Miller has recently suggested this with Brookes being adamant he wasn't moving his date).
At the moment the momentum is with Waterfront but Goodlife still has a huge number of participants.
As for traffic impacts, the sooner people realize that without people driving or travelling from A to B, the sooner traffic and transit will be less congested.
