Since this is my first time doing two major marathons within a short span I thought I'd do a bit of statistical comparison between the 2 races.
NYC Number of Runners: 50,875
Chicago Number of Runners: ~45,000
NYC Finishers: 50,511
Chicago Finishers: 40,599
As you can see most people who started NYC also made it to the finish line. Cooler temps may play a role here, but I also think the heavier crowds of cheering supporters also helps out.
NYC Men: 2:10:59
CHI Men: 2:04:11
NYC Women: 2:25:07
CHI Women: 2:24:35
For the men it is easier to see that the tougher conditions cost some time for the pros. The NYC course is hillier and the wind conditions were brutal. For the women we don't see as wide of a gap, although that could be due to a fierce battle for first that saw a gap of only 3 seconds.
My Own Numbers:
I didn't feel the greatest for Chicago and gutted that one out. I felt a lot better for NYC, but found the course and wind tougher to deal with. The other limiting factor in NYC was being placed in Wave 3 and dealing with thick crowds of people and limited room to run. I decided to just hang tight during the race and have fun with it and not over exert myself.
Chicago 1st Half: 1:50:01
Chicago 2nd Half: 1:59:50
NYC 1st Half: 1:56:07
NYC 2nd Half: 1:59:47
As you can see I ran the 2nd half of both races with remarkable consistency. The first half is where all the difference was made. Chicago I was trying to gut out a good time and NYC I just rolled with the day. I'm more impressed with NYC since the 2nd half there seemed more hilly, that or my legs just got tired and I felt the inclines a bit more.
My 5K splits are a lot more even from NYC than Chicago. You can see where I basically hit the wall with the splits in Chicago whereas with NYC I hit more of an incline and just faded some. I did manage to find a burst of energy for a late push in Chicago, but my legs were pretty taxed by the hills and I just didn't have the same late push in NYC.
Looking back at the numbers and the factors for each race I feel like I actually ran NYC much better than Chicago in spite of having the slower time. I was more consistent and felt stronger throughout. If the course had been flatter, less windy, and less crowded I would of ran faster than my Chicago time for sure.