What location do you prefer for visiting gals?  

Depends on where you want to be.   Most stick to O'Hare area or Schaumburg.   But lately I have been seeing ladies host in multiple locations, downtown and O'Hare or Schaumburg.    Downtown is difficult because of the parking challenges.

i love downtown for daytime visits... it's the best because i'll get a nice downtime break around lunch or early afternoon.
I've noticed there have been more providers available in the area!  O'hare is just a bit out of the way unless i'm taking a full day off work.

When I drive down for business either works.  O'Hare, Glenview, anything on the 294 corridor works as I am driving south.  When I have business on the west side Schaumburg works.  Chicagoland is SO big.  One thing I have not done is go downtown.  

I like downtown heads-and-shoulders above other locations.  Because public transit.  I can just hop on a Metra, transfer to a CTA bus, and discreetly come to the hotel or condo.  With driving to, say, Schaumburg, I'd be paranoid not only about getting busted, but about getting my car impounded too.  Plus, I like to walk to a nearby bar after my session, and drink a celebratory beer.  That's easier to pull off if everything is in walking distance, rather than if you gotta drive everywhere.