Both airports are about the same distance
huh?
well... I guess if you consider that you can take the freeway the whole way from O'Hare, then I suppose the driving times are about the same... but distance-wise, O'Hare is literally twice as far away (based on my road atlas).
Midway does usually have lower fares (due to the presence of AirTran and ATA Airlines), and is an easier drive (just take Cicero south to 159th, to Halsted, or take Cicero south to the toll road, and get off at Halsted). If you fly in to O'Hare, you have to fuck with 80/94 -- which is kinda hit-or-miss, in my experience. Given the choice, I'd pick Midway every time.