CloudDriver wrote:
... No mountain driving involved.
...
no mountain driving - in the Utah portion. But there isn't any on I70 to US191 either, is there?
I70 west of Denver is the quintessential example of mountain freeway driving. I've also seen mention of construction on this section. And the I70 route involves Denver traffic. I've also seen complaints about the state of I70 in western Indiana.
But US191 south from I80 also has mountain driving, while I80 - I15 - US6 is a circuitous route around that.
I80 - I76 - I70 would be my choice. Traffic around Chicago and Denver are minor considerations on a drive of this length.