I'm currently starting to think about a fall marathon and was looking for some opinions on larger marathons.

I've done 4 marathons, and all them had under 2000 participants.

Chicago came up as a possiblity (some friends are doing it, BF has a brother there, I have a sister in Milwaukee so it would be a fun trip). But I'm a little nervous about the idea of being surrounded by 45,000 other people. (My last marathon was 3:54 so I would qualify for one of the start corrals which would help some.)

Any thoughts on larger marathons, or on the Chicago marathon?

Thanks