Have stayed at both a number of times. The Ren used to be something else- a Crowne Plaza? I now do prefer the nearby Hilton Suites, or even the very nice Sheraton Four Points (converted Wyndham). If I had to really choose a Marriott property, I'd probably go for the Courtyard in Oakbrook Terrace.

At this Ren they have now put chains on the little balconies of the corner rooms, so you cannot even step out onto them anymore. The balancing fact is that from this property you have a number of nice restaurant choices a short walk away at the mall (add at least another 5-10 minute walk if staying at the Marriott; if staying at the Courtyard, it is a drive).