I would stick with downtown, O'hare, and Schaumburg.
Each has it's own advantages and disadvantages and many times hobbyists are congregated around those areas because they are large corporate areas. O'hare is in the middle between them and of course easy access for you from the airport.The information I've been able to find seems contradictory.
On the surface both areas seem OK; huge luxury and business class hotels; between the two areas something like 70,000 in daily visitors and.or employees;etc.
But there are also several posts on boards like City Data and Reddit that would suggest maybe not everything is how it seems.
I guess for me, the main question today is whether the area is a "go" or a "no-go" for hosting
In most cities I visit there are tons of hobbyists whose schedules and/or alibis don't allow them to make it into the city.
I'm sure that's true here too.
I would stick with downtown, O'hare, and Schaumburg.
Each has it's own advantages and disadvantages and many times hobbyists are congregated around those areas because they are large corporate areas.
O'hare is in the middle between them and of course easy access for you from the airport.
but I think that the info that I shared with you can be quite helpful. 
We are not in Syria. Sometimes "go" and "no go" and "safe" are code words for an ethnicity other than white. Many folks are scared of their own shadows. This is a large city and crime can happen and does happen anywhere. Be aware of your surroundings, where ever you are. Having said that, for a metropolitan area of several million residents, it's pretty safe. McCormick and the Medical Center are fine. Born and raised here.
You really need not worry about this sort of thing. If you know who you're seeing, and they are men in good standing, your hotel choice is really not relevant.
the loop, mag mile, Gold Coast, river north. These are all areas in Chicago that are easy to access via public transit and have potential to net you more lunch-hour clients. O'Hare incall will net you both suburban and city dwellers, and Schaumburg is a pretty good halfway point between the city and the burbs; you won't get many city folks out there though.
I'm not sure why you'd want to set up shop in the medical district or near McCormick unless there was a conference going on near either of those places.
Keep in mind that Chicagon is a very last-minute city; setting yourself up to capture those last-minute and same-day appointments might be worth your while.
Both are gentrifying areas. That means lofts and latte shops are gradually replacing warehouses and liquor stores. They're not upscale, but they're headed in that direction. McCormick place is a bit farther along. You should even be OK going outside during the day; at night, stay in your hotel.
I'd recommend McCormick place for your situation, as far as potential clients are concerned. It gives you better access to business conventioners and wealthy South Loop residents. Medical District has doctors (who may or may not be hobbyists), but also a large students population of nearby UIC (who usually aren't a target market for most providers).