Having driven I-80 and I-70 many, many times, I'd suggest I-70 to Indianapolis, then N on I-69. I-80 has to go through the Greater Chicago area, tolls, traffic 24/7, and most likely orange barrels. If my wife didn't have roots and relatives in the Chicago area, I'd never put it high on my list of places to drive my RV or a car. I've spent hours sitting in traffic jams in the Chicago area. Even jumping down to alternates is bad because everyone else does too.
Bob & Donna
'98 Gulf Stream Sun Voyager DP being pushed by a '00 Beetle TDI