My vote, IU of course. 
Illinois is probably “higher ranked” in most polls. US news has it 52 for U of I vs 90 for IU. U of I has an engineering program which is probably one of its stronger programs (IU doesn’t have engineering). If business is your thing, then I think IU wins that battle.
IU is a better campus, in a better town, in a better state. Bloomington is a great college town. And Little 500 is a blast. Period end.
U of I is feeling the constraints of IL’s dire financial situation. They will deny that it is hitting the classroom, but it is obviously hitting the grounds and structures – lots of deferred maintenance (that’s what we saw on our summer visits). Champagne/Urban is kind of dumpy. It’s a good in state option if finances are an issue.
My kid saw both and chose to apply to IU and put U of I on the “never mind” list.