Illinois/Indiana natives: need trip advice

[Chevy454]

I'm headed to Martin, Michigan for a race in a few weeks, and I'm debating just how to get there. I've gone to Stanton through both Chicago and Indy, but I am undecided which is better. I always go to St. Louis and over, it's just a matter of where I go from there. From St. Louis, Mapquest said 456 miles (7 1/2 hours) to Martin through Chicago, or 511 miles (8 1/2 hours) to Martin through Indy.

So, any of you Illinois or Indiana natives got any tips? My main worry is that I will be rolling into Chicago about 5pm or so, right in the middle of rush hour, in a crew cab TopKick with a 46ft 5th wheel...not exactly the perfect commuter vehicle.

So, is there an easy way through or around Chicago other than Indy? Is 31N out of Indy decent?

How would YOU go?