What I notice is that every area, and every type of area, caters to different clientele.
Downtown is great for traveling guys who fly in and don't have a vehicle. It's great for a business man for a nice long lunch break. Especially if the girl can track conferences & events.
During big conference dates and events, hotels can be super expensive, but vacation rentals aren't as high as hotels, but much nicer in my opinion.
I get a ton of out call requests to the loop and Gold Coast.
If you want to do a dinner date, budget in a few hundred extra for parking, cab, etc. There are a ton of great places to eat, comedy clubs, blues bars, just... Everything.
So I'm partial to the city, although suburbs are extremely convenient as well for a group of people. The north neighborhoods are great for those who like city living without all the hassle.
So, it depends what you are targeting. All areas, if done right, can be very profitable. You just need to know what's up in that area.